Carol - Regarding BG - I think he really is. The fact that he didn't develop the tools isn't the point. He made the PC platform accessible to PEOPLE. He put more power into people's hands than anyone else. TI. Commodore. Atari. Amiga. Maybe good system, but DOS and MS-DOS is what really made computing a home thing. What was there before that? Different flavors of UNIX? That nobody could afford?
AS-400, IRIX, HP-UX, Solaris (a long time ago) and all those others just weren't something that anyone could run.
MS still supports its small developer community a great deal. Bill started that and he should get credit for it.
On top of that, he's not one of the most generous - he is THE most generous man on earth. I don't see Larry or Steve doing anything like Bill does. He might not be eligible for sainthood, but he's darn close. Ummm... Maybe I should strike that... 
-Renegade
Sorry the BG sainthood is a bit too rich for me!

Actually following your argument you could really argue that IBM are really responsible because they made the personal PC accessible to the masses and commissioned the writing of MSDOS. I don't think they really expected MSDOS to become quite so dominant the way it has or Bill Gates wouldn't have got the job.
MSDOS is another story - BG didn't write it on his own - in fact there is a large body of opinion that there wasn't much in MSDOS that wasn't ripped off directly from CP/M and UNIX (not that BG would admit that - but if others did with Windows today what he did with CP/M you can bet your life that they would be in court).
As for generosity .... I suppose it is fairly easy to be a bit cynical about this. BG may be very generous but don't forget the story in the bible about the "widow's mite". It is really easy to give huge amounts of money when it is a tiny proportion of a huge and rapidly growing fortune. A lot of that fortune has been made by good business sense but quite a sizeable chunk has been made by sharp practice, predatory trading and pure exploitation.
I am sure there are some genuine motives but BG's giving is (at least partly) an element of the PR spin exercise to try and make MS look respectable. After all the company has been repeatedly convicted of illegal trading practices and anticompetitive behaviour on most continents and shows its democratic principles by often choosing to ignore the courts, and even national/international, rulings on such matters!