All sorted. I went back into the BIOS after installing win7 32bit, changed the drives to IDE and rebooted. When it tried to install all the drivers the BD drive came up with a fail, but with a different error message - said it wasn't connected. Not quite sure why, because it had to be connected for the PC to recognise it in the first place. Anyway, I changed SATA cables and plugged it into a different port on the motherboard....and it worked.
I've just reinstalled Vista (not impressed with win7 and can't see what the fuss is about, and I prefer Vista for the toolbar etc), just installing drivers and different bits, but the main thing is.....IT WORKS
Thanks all for your help...lucky I didn't press the "buy" button on ebuyer for a new drive..."just one more go to get it working"

Result!