you are changing the entire chipset (motherboard), you definately require windows re-installation. though in some cases, it will work, but you'll have so many problems afterwards that you'll curse your hardware.
also, windows while installation extracts the necessary hardware architecture files out of the packets, while you'll be inserting a new system into existing installation, where the nVidia board doesnt comes with Southbridges. consider the possibilities of problems afterwards.
Intel Core2Quad 2.66Ghz 12MB L2-Cache
4096MB DDR Kingston Hyper-X
XFX 9600GT AlphaDog
Seagate 2 X 320GB SATA2
LG L246WH Flatron 24"