SP3 Help Centre Lost

After installing SP3 the Help Centre button in my start menu no longer finds the file, just get a message "helpctr.exe not found ". I can find several copies of the file using search, anyone know where I should copy it to so that the menu picks it up?

 

Thanks for the response Arie,

Ran sfc /scannow, it took over 1 hour to run and didn't bring up any file messages at all. After the scan the problem is the same! Any other ideas? I'm getting close to going back to SP2 using restore point, this SP3 installation just doesn't feel good.

 

Found a quick fix, ran a search for the exe file then manually put a key into registry so start menu button for help & support now works OK. Still not happy with SP3 though, keep wondering what else I'm going to find wrong!