Go stepwise now.__
Disable your old HDD, plugin your sata 250.In bios enable Enhanced sata mode.
Set first boot device your Cd-rom/rw
Boot via xpsp2 cd. (first verify that your cd is GOOD, try on other machines).
Press F6 to install sata drivers (it may prompt for your mobo cd/floppy)
thereafter, delete all partitions and create fresh ones.
Then wait further.
if everything goes fine, cool!! else Upgrade your bios. n that'll def. solv your probs.