If you plan on playing any games, stay away from NT4. NT4 is a fine corporate workstation OS, but it pretty much sucks ass for a home PC.
I had this problem with my PC at work with XP. It went cruddy on me twice. I have switched back to Win2K and have had no problems since. I use XP at home with no problems. Either one is good, but XP just seems to dislike some configurations right now.