When I used Spinrite, it took over a week on a 250GB SATA drive but I managed to get everything off it afterwards. It appears my drive's problem was simply unmapped surface defects. The symptoms were that XP would take a long time to boot and, if it booted at all, would BSOD within minutes.

ISTR Spinrite finding a lot of problems in 'patches' on the disk - my layman's diagnosis led me to thinking it was probably just one 'physical' area of the drive with a surface defect even though it appeared to be 'logically' all over the disk.

That drive is still in use 2 years later as a secondary 'dump' area and with no apparent problems.