This is the official repair tool for the MechWarrior 4: Clan 'Mech Pak, which fixes a problem with its content not appearing in MechWarrior 4: Vengeance and Black Knight.
When you have downloaded the repair utility, make sure you have the appropriate 'Mech Pak CD-ROM in your CD-ROM drive, and double-click the file to launch. You will see a DOS window appear while the SafeCast license is verified and repaired. Once this window closes, remove your 'Mech Pak CD and place your Vengeance or Black Knight CD in the drive and launch the game. The 'Mech Pak content should now be enabled.