CTD Issues

Can someone explain why this problem happens.When running FS2004 it sometimes just exits itself for no reason and you are just looking at the desktop.No error message or anything. Ive read it can be caused by overheating or hardware problems.I dont think i have any of these as the computer otherwise works fine.Think I might re install FS2002 as it seems to be much more stable.FS9 seems to be plagued with CTD issues.I have all the XP sevice packs plus the FS9.1 Update installed.Doesnt happen all the time but is very annoying when it does.I can live with the poorer graphics of FS2002 if it runs more reliable plus i have plenty of Addon airports and planes to add to it.Plus you get better FPS than FS9 on todays systems.This has probably been asked before but can anyone shed any light on it.Many thanks