I had the same problem, and the hotfix had trouble working for me at first- not because of the C:\ or D:\ directory, but rather that Inquisit was installed in C:\Program Files (x86)\Millisecond Software\Inquisit 3 not Program Files. Even when copying from the path name from the folder properties this x86 was edited out, so do be careful of the pathway. Once I fixed this, and then restarted media lab, it worked.