Later this afternoon, BoomTown will be front and center–well, I will probably get seated on the far side and way back–for a speech to be delivered by Microsoft CEO Steve Ballmer at Stanford University’s Memorial Auditorium on innovation and entrepreneurship. Part of the Entrepreneurial Thought Leaders Seminar, it is aimed at students there who are looking for some advice from tech’s big dogs.

Ballmer is, of course, all that, with a blustery bark and an occasional bite.

Of course, he’s probably channeling a more charming demeanor in another meeting sources say he plans to have with Yahoo CEO Carol Bartz on this visit to Silicon Valley.

The second since Bartz took over Yahoo in January, it’s about whether or not the pair should make nice after a long period of useless acrimony, and strike a significant search and advertising partnership.

Many close to the discussions, which have been going on seriously since late March between small teams from both companies, said that how the pair get along and whether they can actually pull the trigger together is all that matters.

Rapport is key, especially since such a deal has been exceedingly complex to figure out.

The latest idea is one in which Yahoo (YHOO) would take over both search and display advertising sales and Microsoft (MSFT) would run the tech for both behind the scenes.

It’s not clear if trading other assets–-such as content–-or a large investment in Yahoo by Microsoft are being considered too.

If struck, such a deal would be a major shift for both companies in their business focus and would also tether them tightly together to better compete with Google (GOOG), which overwhelmingly dominates the lucrative search market.

Still, sources said, there is a lot keeping Microsoft and Yahoo apart, most especially a profound wariness over controlling key technologies and tense history between them.

In addition, execs on both sides–such as Microsoft digital head and former Yahoo tech exec Qi Lu–are treading carefully about every item, unsure of how so many ties would be handled.

“Could we fire Microsoft if they did not perform?” asked one Yahoo exec. “Or would we be stuck without control over our destiny, if it all went south?”

For her part, sources who have spoken to Bartz about the recent discussions with Microsoft said, she has remained resolute in not giving up too much power to Microsoft.

Microsoft is also gun-shy after its disastrous takeover attempt of Yahoo failed last year–with Ballmer loath to make another such epic mistake in trying to turn around the software giant’s lackluster digital efforts.

“He simply does not want to look stupid again,” said one Microsoft source. “So it weighs on whether he has the guts to put himself out there.”

That’s ironic, of course, since his Stanford speech today is on entrepreneurialism and innovation, which always require an ability to use failure as a way to move forward.

The question is, can Ballmer walk that talk?

But–as many readers have requested–they will all be available in their entirety in this column.

Here’s Part 3 of 4 of an interview Walt Mossberg did with Sony Chairman and CEO Sir Howard Stringer. (I am posting one video part of the discussion with Stringer every day this week, starting Tuesday and concluding tomorrow.)

Sony (SNE) has been under enormous pressure to innovate and compete better in all its many businesses, and the consumer electronics giant still has not proved that it can knit them all together into a cogent whole.

In this video, Stringer talks more about craplets, discusses digital music players, including the iPod and Walkman-enabled Sony Ericsson cellphones, and takes questions from the audience about YouTube and the challenge of maintaining innovation and entrepreneurialism at a huge multinational company.