Red Alert 2 Map Editor Help

[Robe]

Not sure if this belongs in PC Cames or PC Troubleshooting but here goes...

I have just downloaded Final Alert 2 (Red Alert 2 Map Editor) and when i try to open it I get the error message: "Red Alert 2 is not correctly installed (ra2.mix could not be loaded)"

Any suggestions on fixing the problem? Also if it makes a difference, its not an original copy of RA2 its one my friend copied for me but everything else seems to work fine.

Any help would be appreciated.