It's making that nice loud whine which screams "my bearings! my bearings!", and is vibrating more than a disk should, which implies the platters are now unbalanced. Xcopy is currently involved in a list-ditch attempt to pull all the files off. It's not as if there's anything important there, but I'd rather like to keep the contents of my \Temp folder. And having my Outlook calendar in one piece would be nice.
The file copy's been running for a few hours - 20 gig takes a while to copy at the best of times, and a lot longer when the source is throwing errors at you. But I'm winning, at last.