A lot of people tried to install a new car, mod, map or something else to sanandreas. After starting the game, it crashed and they didn't made a backup of the old files.
This is the part, where this program can be used:

1. Select your SanAndreas Directory
2. Select your DVD-ROM Drive
3. Choose a category on the left side
4. Choose a file you want to recover
5. Put your SanAndreas DVD in your DVD-ROM Drive
6. Click 'Recover' and wait a few seconds/minutes
7. The file has been overwritten and the game can be started (modded) again

Hav a lot of fun.