OK-the FSX Repair-doesn't it reinstall everything in addition to what is already on the hard drive, because it says on the description "Reinstall all program features installed during the last installation" or something like that. Does it take 15 GB again? I have a TINY hardrive, so I don't really have 15 GB to spare. Is this close to what happens, or am I that naive? I started to do it a couple days ago just to see what happened, but it froze, so I quit. What exactly does the repair do? :-/
Small had drive may be a problem if it allocates space and the space is not available. All it should do is replace the critical files and go through the rest. I do believe if it finds files that are mismatched in type, size or date it will overwrite them with the ones from the disk, then clean up the temp space it used. It will not install another 15gb of files, just temps which it dumps.
The freeze may have been related to low disk space or possibly the issue at hand but if the reset tool said it was successful, I would do as Doug's link suggests and try the repair install again. Make sure you put the files back which you backed up earlier from my suggestion and just for giggles perhaps after doing that you should run the reset tool again. Then reboot and try a full repair of FSX.
It may take some time. If the processes freezes again I would suspect low disk space if your hard drive is very small and has less than 20gigs of free space available before you startwd the repair.