This week, I tested the H-P iPAQ 510 Voice Messenger from Hewlett-Packard, H-P’s first real cellphone and a big name for a diminutive product that is due out in April or May for around $300 to $350. Attempts to add phones to H-P iPAQs in the past usually resulted in clumsy interfaces, giving the feeling of a phone crammed into a data device.

The H-P iPAQ 510 Voice Messenger from Hewlett-Packard.

This new 510, however, comes across as the opposite: a gadget with smart-phone capabilities that is limited by its small size and lack of useful physical features, many of which are included on other smart phones. H-P has tried to compensate by using a built-in voice-recognition system that enables email dictation and reads emails aloud, but this is no substitute for a keyboard. Overall, the product is very disappointing.

Emails you dictate are sent as audio attachments, a technique that doesn’t allow the recipient to print the emails, save them as text, or copy and paste the message contents into other emails or documents. The robotic voice that reads emails you receive is bad. And using voice commands to enable the phone’s functions brings forth separate frustrations.

The iPAQ 510 is smarter than it looks: It runs on the new Windows Mobile 6.0 and can use Wi-Fi to provide a notably fast network connection. However, as if to drive home its phone functionality, the 510 disguises its smart-phone brains under the shell of a cute, stylish, basic cellphone. Its edges and keypad are black and the rest of the phone is gray with a handy 1.3-megapixel camera on the back side.

This gadget’s emphasis on looks comes at a price: It relies solely on its numeric keypad rather than a full physical or virtual keyboard, its relatively small two-inch screen doesn’t have touch capabilities and it doesn’t use a built-in scroll wheel or track ball for fast navigation.

So what’s the point? H-P hopes you’ll forget about this device’s faults when you use its Voice Commander feature to help you speak your way through navigating, composing emails and even listening as emails are read aloud.

But hear this: Even though Voice Commander offers over 20 different commands, it still suffers from the same problems as all voice-operated devices. You can’t use it in a noisy place, tough names (like my last name, for one) are often misheard and voice recognition still takes longer than pressing buttons.

The two email-related voice commands are theoretically the most useful, letting you dictate audio emails into the phone and directing Voice Commander to read emails aloud. But dictated email that you send isn’t converted into text, as one might hope. Instead, it is sent as an attached WAV file, inconveniently forcing your recipient to first open an attachment and then play your email aloud. And like all audio files, this email attachment isn’t as versatile as text, which can be printed, copied, or saved as a separate document.

What’s more, Voice Commander’s email dictation and read-aloud features work only with a Microsoft Exchange email address. So, if you’re using a Google Gmail or Yahoo email account, for example, you’re still stuck using the phone’s numeric keypad to write out messages.

The H-P iPAQ 510 Voice Messenger has a few upsides. It runs on the new and slightly improved version of Microsoft’s mobile software. It can easily hop onto any nearby Wi-Fi network, which worked quickly and efficiently in my tests. And H-P boasts that its battery will last for 6½ hours of talk time, about an hour longer than the closest competitor’s estimate.

But these good qualities are overshadowed by the 510′s poor design. I dozed off while holding my thumb on the “down” directional key to skim through lists of emails — it took much longer than using a BlackBerry scroll wheel or a Palm Treo touch screen. For certain Voice Commander functions, I had to repeat my command twice and then confirm that my command was correctly heard; more than once I gave a command that was entirely misunderstood.

I used many features of the iPAQ 510, focusing on Voice Commander to see if it made a significant difference in the product. Unless you have your phone’s earpiece attached, Voice Commander automatically barks, “Say a command,” through the phone’s speaker. I spoke a command by choosing from the on-screen list of statements, such as, “Call at ,” for which I could say, “Call Katie Boehret at work.” Voice Command repeated my choice, asked me to confirm that it was about to do the right thing, and proceeded.

But a lot of basic cellphones already have a voice dialing feature built in. So I focused especially on creating audio emails, speaking my email into the phone just as one might if recording a voice reminder. When I finished, the system played my voice email back, asked me to confirm that I wanted it sent, and emailed the message.

Voice Commander will also read emails and SMS text messages out loud. By opening Voice Commander and saying, “Read email” or “Read SMS,” unread emails or text messages were read aloud by a robotic female voice that was lifeless, barely understandable in some cases, and nowhere near as warm as the voice I heard last week in an Audi’s car GPS system. I responded to emails by dictating audio replies; you can’t use Voice Commander to dictate SMS messages.

I also used Voice Commander to find contacts, start applications, open a window for composing a new text email or listen to new appointments on my phone’s calendar.

The H-P iPAQ 510 Voice Messenger offers a way to use the phone for Internet calling, but the setup for this is so complicated that it requires help from your geeky cousin or an IT department.

All in all, this new venture from H-P is littered with shortcomings, mostly due to an emphasis on beauty over brains. The iPAQ 510 is powerful and fast, especially when using a nearby Wi-Fi network. But if you can’t easily navigate and must rely on a lackluster voice-recognition system, these features are dead in the water. H-P has nowhere to go but up from here.

• MossbergSolution@wsj.com

But what about the other major function of a laptop-viewing and editing Microsoft Office documents? Well, it turns out you can do that, too, on these devices, at least to a point. Currently, you can read Word, Excel and PowerPoint files, as well as Adobe PDF files, on certain handhelds; you can even edit them and synchronize the changes back to a PC.

Here’s a look at how that’s possible, on the three most popular types of smart phones and PDAs in the U.S.: those powered by the Palm operating system, those powered by the Windows Mobile operating system (formerly known as Pocket PC), and the BlackBerry, which uses both hardware and software from RIM.

First, make sure your device has lots of storage capacity, either in internal memory or on a removable memory card, if your device can accept them. (The Treo, the iPAQ and most other devices running Windows Mobile software can; BlackBerry models cannot.) You will need that room to store your Office documents.

Second, I strongly advise those wanting to edit documents to buy a phone or PDA with a full keyboard, rather than one that relies solely on handwriting recognition or a phone keypad. The software for viewing and editing documents does work on devices without a keyboard, but unless you just want to read documents, the process is painful on these models.

You might think that the devices running Windows Mobile software would do the best job of handling Microsoft Office documents because both systems are made by Microsoft. Or you might imagine the BlackBerry was tops at this task because it is bought mostly by corporate computer departments, where Microsoft Office is the application software of choice. But in fact, the best devices for viewing and editing Office documents are those using the Palm operating system, such as the Palm Treo 650. That’s because of a helpful third-party program, Documents to Go, from DataViz, which is packaged with many Palm devices, including the Treo.

Next best are the Microsoft-powered phones and hand-helds, which come with built-in mobile versions of Word, Excel and PowerPoint. Bringing up the rear is the BlackBerry, which can display Word, Excel and PowerPoint files when sent as e-mail attachments, but doesn’t let you edit or synchronize them with a PC.

Palm OS devices. The best smart phone on the market is the Treo 650, produced by Palm and powered by the Palm operating system, which is made by a separate company called PalmSource. While the Palm software lacks the built-in capability to read or edit Office documents, the Treo comes bundled with Documents to Go, which can import and open Microsoft files in their native formats without downsizing them to some special “pocket” version. It also allows you to edit, or even create, these types of documents and synchronize your changes with versions on your PC.

You can get the documents into your Treo or other Palm device either by receiving them as e-mail attachments or via synchronization with your PC. Documents to Go includes a computer program that performs this document synchronization; I use it often on my Treo 650. It displays documents in their actual fonts, including colors and attributes like underlining, bold and italics. Indents and spacing are also preserved. The Treo 650 doesn’t support different font sizes, and it doesn’t include a spell checker. Documents can be opened from, or stored to, either the device’s internal memory or a memory card. You can also zoom the screen to show more or less of the document, especially important with spreadsheets, which often sprawl across the page and can be hard to read when resized to fit entirely on the small screen. PowerPoint files can be edited and synchronized only if you are using a Windows PC, though they can be viewed if you are using a Macintosh.

In my tests over the years, Documents to Go performed flawlessly, better than the built-in mobile Office programs on Windows-powered handhelds. In addition to being bundled with the Treo and some other Palm devices, Documents to Go is available for independent purchase, in several versions, for $30 to $90, depending on features. There are also versions for smart phones that use the Symbian operating system, including models from Nokia and Sony Ericsson. You can find information and purchase Documents to Go at www.dataviz.com [http://www.dataviz.com].

Windows Mobile devices. There are two kinds of devices powered by Microsoft’s Windows Mobile software. Some are confusingly named “smart phones,” though they generally lack keyboards and some key software capabilities, including the ability to edit Office documents. Others are full-featured handhelds, including some with keyboards, such as several of HP’s iPAQ models, the new Samsung i730 phone and the very latest and greatest Windows Mobile device, the Treo 700w.

The new Treo is the first device built by Palm to eschew the Palm operating system for Windows software. While it’s mainly aimed at the corporate market and, in my view, isn’t as good as the Treo 650, the 700w is probably the best Windows Mobile device. On the new Treo and others, you can read, edit and create Word and Excel files, and synchronize them with your PC. You can view PowerPoint files, but not edit or create them.

As with the Treo 650, you can get these documents into your device either by receiving them as email attachments or by copying them from a PC.

While the mobile Office programs on the Windows devices work okay, they aren’t quite as good as Documents to Go, in my experience. For instance, in a recent test I opened a simple Word document on two Treosa 650 running the Palm OS and Documents to Go, and a 700w running Windows Mobile and its built-in Office Mobile programs. Documents to Go opened the program perfectly in its Times New Roman font and sized it so the words were distinct, and the formatting was preserved. The Word Mobile program in Windows Mobile displayed the document in a different font and in a size that screwed up the formatting. And while Documents to Go allows you to create and edit PowerPoint files, Windows Mobile doesn’t.

BlackBerry. The BlackBerry can view Office documents when received as e-mail attachments, but the function is pretty primitive. You can’t directly import documents or synchronize them with a computer. And you can’t create or edit them, even though you have a full keyboard at your disposal.

There is a third-party program for the BlackBerry that claims to allow editing, creating and synchronizing of Word and Excel documents, but not PowerPoint files. It’s called eOffice, made by a company called DynoPlex, and it’s available in versions ranging from $120 to $200 at www.dynoplex.com [http://www.dynoplex.com].

I wouldn’t want to write a long report on a Treo. But in a pinch, I could have written this column on one. And editing a document like this is a breeze. So you really can leave that laptop at home, at least some of the time.

Here are a few questions about computers I’ve received recently from people like you, and my answers. I have edited and restated the questions a bit, for readability. This week my mailbox contained questions about troublesome email attachments and finding a hand-held mobile product that doesn’t include a cellphone.

If you have a question, send it to me at mossberg@wsj.com, and I may select it to be answered here in Mossberg’s Mailbox.

I use a Macintosh, and sometimes when a Windows user sends me an email attachment, it comes through as a file called “winmail.dat,” which can’t be opened. Is there a way around this?

Most attachments sent from Windows to the Mac come through fine, and vice versa. The situation you describe apparently occurs when the sender is using Microsoft Outlook and sends a “rich text” email that requires Outlook to decode. Since there isn’t a version of Outlook for the Mac’s current operating system, it comes through as a useless and mysterious winmail.dat file.

However, there is a free Mac program, called TNEF’s Enough, that can unlock the attachments buried in these winmail.dat files, so you can read and use them. You just save the unreadable attachment as a file on your hard disk, then open it in the free program, which converts it to a usable file or files. I have tested the program and it works well. It can be downloaded at: www.joshjacob.com/macdev/tnef/index.html.

Is there a hand-held mobile product that would enable me to surf the Web and attend to a few emails, using my home’s existing Wi-Fi system? I have several desktops and laptops, so I don’t need another computer, and I don’t want a cellphone. I just want something less cumbersome than a laptop.

A:Yes. Palm, Hewlett-Packard and others make PDAs (personal digital assistants) that don’t include cellphones but do include Wi-Fi receivers, email programs and Web browsers. Palm’s new $299 TX hand-held is a good example. So is HP’s iPAQ rx1955, which also is $299. Both have Wi-Fi Internet connectivity, large, bright screens and built-in email and Web-browsing software. The H-P is lighter, but the Palm’s screen has higher resolution. www.palm.com/us/products/handhelds/tx. Information on the H-P is at www.hp.com.

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Because of the volume of e-mail I receive, I can’t routinely answer individual questions by e-mail, or consult on individual problems or purchasing decisions. I read all questions I receive and select three each week to answer in the column.

Write to Walter S. Mossberg at mossberg@wsj.com