FS2002 not loading after installation of FS2004

I Got Prolems--Need Help

Had FS 2002 worked great, got FS 2004, worked great except for a few glitches and after loading 2004 I could no longer access 2002. No biggie but a lot of the aircraft didn't work on 2004. I had too many aircraft folders so I uninstalled both and reloaded 2004 and started from scratch. Alas! I have downloaded about twnty aircraft and only two of them work. The others are in the aircraft folder but do not appear in the actual list when selecting for flight. Is there something I am forgetting or maybe overlooked? Can't figure out what is going on. Maybe I should
uninstall again? Stumped