Unless you are a system builder with a license agreement, I don't think its possible to buy an OEM version by itself, they are to be sold ONLY with a PC.
Of course, you can always try finding one dor d/l somewhere...
Intel P4 2.4B, MSI 645E Max-U Mobo, 1GB DDR333, ATI R9800PRO 128MB, TT PurePower 420W, SB Live 5.1, Samsung 120GB, Maxtor 120GB, LG DVD+-R/RW, WIN2K PRO SP4