I also have installed windows XP Pro x64, but didnt/have not run into such a problem, still, i would consider burning an ISO of the CD and retrying, if the problem still presists, i would reccommend tech support from microsoft, if all else fails ask for another copy since it appears your copy is faulty, you might even be able to get another to download via email, ect. Hope Ive given you something to try at the very least.
Lata Foolio
Current Specs:
Foxconn K86100 Mobo
Nvidia 7600GS 512MB
AMD 64 3400+
1GB of PC2700 RAM
160GB HD
Lite-On DVD-RW Drive
Windows XP x64 Bit
*All this decadence in an open window, burgandy case, with sparkle bright blue LEDs speckling light on my ravishing bundle of technology. *