Is the folder for the 777 under the Aircraft folder also gone? If it is, you need extract those files off the installation CD's. I don't know how to do that, but maybe someone else here can give you detailed info. You could also just rename your current fs2k2 directory(the whole thing) to something like fsold, then reinstall FS2k2. After reinstalling, move the 777 folder to the aircraft folder in the fsold folder. Once it is copied to your "old" FS installation, delete the new one you just installed and rename the old one back.
If the folder is still present, something probably got hoses in the aircraft.cfg file. Check this against a working aircraft.cfg like the one in the 737 folder.
Hope this helps,
I reckon your re-installation tip is the one to go for, I've checked everything else, including the aircraft.cfg file.
It'll take some time but I reckon it'll work.