Low level format...
Hi,
I had a similar problem a couple of years back, the drive reported a bad sector somwhere where for some unknown reason windows insisted on having something stored.
A normal, i.e. DOS/Windows, format would not fix it. I had to get a low level format tool from the drive manufacturer's website. It took about 3 hours to test and restor the drive to a factory fresh condition but it has worked perfectly ever since!
Best of luck.
Memetic