You are not limited to one install with OEM XP packages. On the second install, on the same machine, you will need to call mirosoft and manually install. Once you've done that they reset your install quota to 3 and after the third new install you will have to call again ad nasueum. OEM is the cheapest and best way to go with XP!
Noli Nothis Permittere Te Terere!!
EVGA 680i, Dual EVGA 8800GT'S (650/950), 4 gigs OCZ DDR2 1066, Intel Q9450 at 3.8 Ghz, Koolance Water Cooled, Dual Plextor16x DL DVD+/-RW. Dual WD 250gb 16mb Cache Sata 3.0. 3DMark06 score = 19,168.