The system I'm using right now, I built 5 or 6 years ago and it runs everything I have thrown at it. It started it's life with Win98, moved up toWin2K, then finally XP pro. I have also had several Linux distros installed at various times. The trick is to do your homework and get the best price/performance ratio you can afford.
Any os as a seperate purchase cost way too much.Mac os is expensive too but not quite as bad. Best deal is a pc you can afford and later max out the memory, etc when those parts are on sale. One of the stores has a special on a 2ghz minitower with XP for $199 after rebate ,the same cost as a XP os package by itself!!!!! Add your old but servicable monitor....I just can't justify the os upgrade expense .