Thanks, I haven't tried that, my problems are happening before I get to that point, I'm thinking it's related to the hardware or BIOS.
Following the advice above I have either
1) custom installed W7 from the DVD on the 500GB drive, which then calls itself "C", and gives the error "oxC000000e". (And deson't fit with my existing drive names of C (Vista) and D (XP) on the 250GB drive)
2) the message when attempting a custom install from the DVD on Vista of
"
Windows cannot be installed to this disk. This computer's hardware may not support booting to this disk. Ensure that the disk's controller is enabled in the computer's BIOS menu.
"
but nothing in my (Phoenix) BIOS that lists disk controllers or enabling them.