"Delayed Write Failed"

I run Windows XP SP2 on a Dell Inspiron E1705, and my external hard drive (SeaGate Free Agent Pro 500GB) is almost always attached via USB. About a month ago it started giving me this error while I was listening to music loaded on the external, simultaneously locking up Firefox and Winamp. The error claimed that the Delayed Write failed and that whatever data was being written (always D:\$Mft) has been lost, but I wasn't copying anything to the drive at the time. After the first episode I let my computer sit alone for awhile, and when I went back all was well. But the other day it started again, but became progressively worse. It culminated in my drive making a horrible super-fast spinny noise while nothing was accessing it, sliding around, and then stopping. Now I can't access it at all. What can I do to recover my data and prevent this from happening in the future?

No I haven't. The only thing I can think of like that would be when it was in my checked luggage while traveling to Okinawa.