You would need to add the registry entries for the game.
Copy and paste the text that suits your OS from below into notepad, then Save As -> All File -> FC3.reg.
Double click your new FC3.reg file and yes ok when prompted.
For Win x64, first change "InstallDir" to your Far Cry 3 path (be sure to use double backslashes in the path):
Code:
Windows Registry Editor Version 5.00
[HKEY_LOCAL_MACHINE\SOFTWARE\Wow6432Node\UBISOFT\Far Cry 3]
"InstallDir"="C:\\Games\\Far Cry 3"
"ExecutableName"="bin\\FC3Updater.exe"
For Win x86, first change "InstallDir" to your Far Cry 3 path (be sure to use double backslashes in the path):
Code:
Windows Registry Editor Version 5.00
[HKEY_LOCAL_MACHINE\SOFTWARE\UBISOFT\Far Cry 3]
"InstallDir"="C:\\Games\\Far Cry 3"
"ExecutableName"="bin\\FC3Updater.exe"
See how it goes.