Just built a new P4 system. Asus MB, memory, and processor all purchased via motherboards.org. Everything can be customized, plus they will install all above components and test them for 24 hrs prior to shipping. Great tech support. Complete line of Athlon chips and boards too.
long time ago On windows 98 I ve done that before. Celeron 566Mhz (overcloced to 850Mhz ) to Athlon system but I had to start from formatting my HDDs (there were recognision problems) I think on Win XP (im not sure on Win2k) You can do it without reinstalling the OS I really love WinXP will gain connection perfomance dramatically too. I dont know how long you have been using your PC but its good if you format your HDDs once in a while. (if you have important data just burn it to CDs :>)