Rick,
Microsoft is a huge company, but there is no way they could buy Sony, unless they want to end up in a life time of debt.
Sony is a huge company, they own alot of media companies as well, Colombia Pictures, Sony Computer Entertainment, Tri Star, Sony Pictures, Sony Music, Metreon, and many more companies, I think MSFT wouldn\'t even think about trying to attempt to buy Sony. Also Sony owns there on broadband company in Japan, Sony is a huge company, most of the things they own are in Japan!
I remember a poster at the IGN boards last year posting all the companies Sony owned, it was like 15 or 20 of them I think, I will try to get the list later.