In a nutshell: healthy external SATA drive (functions fine in another desktop) connected to old Compaq 'presario' via a PCI SATA card (ALi M5281). Compaq internal drive (dual booting XP and Ubuntu) is also a SATA drive running from same card. I connect the external drive in order to make a partition clone. It is recognised in the BIOS and by Ubuntu and I create a folder ready for the clone image. I restart the pc, first loading the cloning software (Redo - Backup & Restore) on a live cd. Redo starts loading up as usual, then seems to hang. After a very long time of repeated dots I conclude something's amiss and attempt various key combinations to abort. The escape key produces a very fast screed of print-out, none of which makes much sense to me, and it doesn't stop. In desperation I do a power shutdown. From that point on, despite many attempts, the external SATA drive is not recognised in the BIOS. Whereas before at the "Identifying IDE drives" screen I got "xxoo" followed by the names of the two SATA drives, I now get the familiar "xxox" and just the internal drive listed.
I've checked the ext drive again on another pc and it's fine. I've checked the connections and cable and all seem good - after all, it worked a couple of hours ago. I've checked nothing's got changed in the BIOS. Everything else on the Compaq seems fine - Ubuntu booting up as normal. So, could the power shutdown have caused something to go wrong, or was that just a coincidence? Should I be removing and reinstalling the SATA card as a next step? I'm rather out of my depth here, and the problem is: it's not my pc, it's my partner's ... and she gets home tomorrow!! Any advice, suggestions, troubleshooting tips would be very welcome.