I haven't been able to find a post that describes my problem, and it's
a strange one.

I've got a problem with disk READS on one of my hard drives in Vista.
It popped up seemingly out of nowhere.

My system drive is on a separate hard drive and it seems unaffected.
My D: drive (data drive) is where the problem lies.

Folder-to-folder copies are taking about 4 minutes for a 700 MB file.
On the system drive, they take about 35 seconds.

Copying the file from C: to D: also is fast, so it doesn't appear to
writing to D:, only reading.

My Computer is set to not use icons or thumbnails.

I've defragged the drive to no effect. Also did a virus scan with
nothing found -- to be expected on a data drive.

Any clues?