ERROR CODE -1309. AARRRGH.

Since starting to use Parallels I know have files that are much much larger than 4 GB--the virtual disks. Currently one of them is sitting at about 18GB, and unfortunately I'm running into this wonderful error:

Sorry, the operation could not be completed because an unexpected error occurred
(Error code -1309).

I did some browsing around and it turns out there is a 4GB file limit on FAT32-formatted drives. Ugh. I put it in FAT32 so I could see it with the Mac, but of course that now creates the problem of the virtual drive. I don't know what to do really. I suppose I could find a file-splitting utility somewhere... Ugh.