I was able to get it to work perfectly, and I think I know how it will work on all computers.
I was getting the same "Error: Hard Drive Full" error and tried the unofficial patch & QFixApp. Neither worked. However, when using QFixApp, I saw the 2GBFreeSpaceEx thing and thought that it might work if I got my hard drive under 2 GB, it would work. Lo and behold, it worked fine. So if you can get your hard drive under 2 gigs, it might work. I don't know whether or not this will work for everyone else, but it's worth a shot.