We just got our computer fixed and FOC wouldn't work, however the JCW mod on the original still did. So I tried to uninstall FOC but it wouldn't and I got this message everytime I did (see pic below): I also had the z3r0x version 3.5.
Try going to C:/ProgramFiles/LucasArts/ and highlight your FOC folder. Send it to the recycling bin and delete it. Then try to uninstall and see what happens.