computer ?, operating systems Options

[96bluevert]

ok, so some of you know I am building my own computer and at this time I am gathering all the parts that I need. I will have 4gb RAM (with the intent to expand later), so I know I will want to go with a 64-bit OS. Although I can't decide between Windows XP Pro and Windows Vista. I am used to XP, since it has been on my last few computers, although I have heard that Pro has problems with some older software. I've been reading up online about the differences and which would be a better choice, but it hasn't got me anywhere since half the reviews I read say Vista is the way to go, and the other half say XP is the better O/S to get. I don't want to spend $100+ on an Operating system, just to find out I should have gotten the other one .

so, any advice or experiences you guys have had with these two would be helpful.

also, I am assuming that I will want to get the software that is meant for "system builders"...? There are just way too many options on newegg with a very wide variety in price