The actual file may still be there, it may only be the shortcut that is the problem. If you are just doing a regular backup, go to Start/Programs/Accessories/system Tools/Backup to open the program.
If it is not there, then you should be able to restore the file from the OS disc. Running the SFC file checker is one way of determining if the file is missing. To do this go to Start/Run and type in sfc.