i've used every O/S out of M/S, since MS-DOS prompt, and I have found 2 O/S really worthful to buy, that are 98SE and WinXP, as when I wa using 2K, i use to think that is more stable, but my thinkings changed as when I used XP, as its faster, and light to resources. (though heavy to hard drive)
Intel Core2Quad 2.66Ghz 12MB L2-Cache
4096MB DDR Kingston Hyper-X
XFX 9600GT AlphaDog
Seagate 2 X 320GB SATA2
LG L246WH Flatron 24"