Since you provided zero information in your first post it's difficult to know exactly what the problem is. The more detail you provide, the better we can assist.
1) Is this an attempt to do a brand new, clean install (are you booting to the XP CD and trying to format first)?
2) At EXACTLY what point do you get the error?
3) WHY are you doing a new install?
4) Are you using an original, retail XP cd?
If you think it's ram, here's how to check:
download memtest (
http://memtest.org/). Burn it to a cd using a dedicated .iso burning utility (
http://www.petri.co.il/how_to_write_iso_files_to_cd.htm), make sure the cd drive is at the top of the boot order in bios, then boot to the newly created cd and run the utility.