Do you want to use Vista or Windows 8?
If I can get away with using the recovery CDs then I just use Vista as I know how to use it. Aslong as them CDs work on a new HDD
Can try the links here and download either 32-bit or 64-bit version (they use same key on label underneath laptop so don't need to worry about sticking with 32-bit version if that's what originally came with laptop).