Have you considered that perhaps he spent his career as ruthless business man as a means to an end? It's hard to make any serious change when you're at the bottom of the totem pole, or even halfway up for that matter.
Ah, that makes it ok then. A bit like the mafiosi that give a lot of money to the church on their death bed, it's just a means to an end, so sorry if you're in the way.
Really, Bill Gates has done some good things in recent memory but if you're going to whitewash his crimes because of that then your moral compass is totally out of whack. I'm happy he's chosen to do good later in life rather than to continue on the road that he was on, at the same time I find it impossible to forget how he got to where he is today.
I don't personally know Gates, and I doubt I ever will. If all I have to go by are his deeds (and that's the case), then he's done a lot of good. He could have bought himself huge truckloads of goodwill, much easier than some of the things he's chosen to focus on.