tecknomage

First, Logical Disk = Partitions. C: = Logical Disk Designator for example.

Logical Disk as opposed to Physical Disk, in your case you have Physical Disk HD0 with Logical Disks C: & D:.

Have you tried running CHKDSK D: /F from the Command Prompt assuming your problem is only with D:?

Also, Partition Magic will do repairs.

Lastly, why FAT on D: You can use Partition Magic convert to NTFS without loss of data. But you should repair D: fist.