If this was a FAT32 volume and you did a 'quick format' and you have UNFORMAT.EXE in your c:\windows\command folder, try that. This utility was designed to use the backup copy of the FAT and reconnect the unerased but disassociated file clusters to their original files again. It may be available in the 'oldmsdos' directory of a Win95 OSR2 or Win98 CD.
If you were using NTFS, you'll need specific recovery tools...
You might be able to use a Knoppix LiveCD to track the file clusters and reassemble them too...