I was repartitioning my sons pc but before set up has finished inspecting the system I get error message "the file aic78xx.sys is corrupted" - and set up exits
This is a scsi driver for nt but I am using a jetway v400dbl mobo and a maxtor diamondplus9 ide hdd.(win xp pro)
I have reinstalled windows many times and this has never happened - any ideas

did you try running setup again?
are you repartitioning on a clean hard drive or within windows?
Is the cd dirty? try a different cd if you can?