<<I disconnected that drive and managed to fix the c drive and reinstall xp on it - but if both drives are wired up the machine boots from the wrong one. If I disconnect it untill after boot up and then reconnect it, the computer can't see it.>>
Is this "second drive" an external drive?
FWIW: Any drive which reflects Windows...when booted into...is recognized as the C: partition/drive. The drive reflecing the working Windows O/S...will always be recognized as the C: partition/drive and drive letters for all other partitions may change if a multiboot situation exists.
I suggest you go to Disk Management and take/post a screen shot...reflecting both drives recognized by Windows.
How To Capture And Edit A Screen Shot - http://www.bleepingcomputer.com/forums/topic43088.html/page__gopid__2493350