If you cannot access your disk, either the MBR (master boot record) or FAT (file access table) is damaged.

There is a partition expert named Sven Olaf Mikkelsen who posted utilities that can recover damaged partitions:

http://www.partitionsupport.com/utilities.htm

These utilities reads the entire disk and find each file header and tries to reconstruct the MBR and FAT.

He helped me to recover a bad disk successfully via email. Obviously he is a busy guy and sending some donation can catch his attention better.

A few years earlier, we sent a bad disk to a recover house and it cost more than the PC.