A word of warning about external Maxtor (Seagate) OneTouch USB drives: I have two of them (a 1TB and a 500GB), and both have lost their partition tables in less than a month's span. Granted, these drives are 2 and 3 years old (respectively), but one would expect a drive to retain its data at least for the duration of the 5 year manufacturer's warranty.
After doing a lot of reading, it appears the USB->IDE interface used in the enclosure is of suspect quality. I can unscientifically confirm this, as I have been able to temporarily rectify intermittent problems with both of these drives by replacing aged USB cables (though the cables work flawlessly in other applications).
This problem appears to be quite common, and there are various methods for recovering the data. I have chosen two, and am trying the least invasive first: an open source program called TestDisk, which has a good reputation for repairing deleted/corrupt partition tables (and data).
If this fails, I'll simply open the case and remove the drive, then plug it directly into the internal IDE interface. (The 1TB drive may be a SATA drive, which would be even better.) In either case, the drives themselves are apparently rarely defective, so I'll only lose the portability of the drives, which in this case is not a huge concern, as they are always connected to the server.
These drives have been problematic for the majority of the time I've owned them, and it doesn't seem to matter what OS they're connected to. (I've had them on 3 different machines: XP, Windows 7, and Linux.) I don't believe these specific drives are commonly sold anymore, but still, I recommend that people steer clear of them, as well as their new Seagate counterparts.
For the record, I've never been a fan of either manufacturer (before or after Seagate's acquisition of Maxtor), and only purchased the drives because of their low price point. Once again, the old adage is reaffirmed: you get what you pay for.
Thank goodness all my other drives are Western Digital.
