A few weeks ago a upgraded my PC to a P4 3.2 with 1Gb RAM and 2x 80Gb hard drives

I feel your pain Terblanche as I recently bought a new computer - just for FS9. There is hope, hang on but it will take a lot of work. When I first installed FS9 on the new computer I was getting various CTD's with different addon aircraft and locations. After reading various posts I did the following and it works well for me.1. Uninstall FS9, defrag the hd, reinstall FS9. Now stop!!! DOn't install any FS9 addons. Keep your "fresh" FS9 installation free of any addons until you test it. This could take a lot of time, but it is worth it in the end.2. Now try some the long flights you've done before which had CTD's. Try to recreate it as close as possible to the problem flight - but using default aircraft and scenery. The idea is to try to isolate possible CTD causes. Try flying numerious flights of the type which caused problems and see what happens. If you get CTD's with a fresh FS9 install, then maybe the problem has to with hardware issues. Unfortunately I can't help there, but the hardware forum can be very helpful. If you don't get ANY CTD's with the fresh install, goto step 3.3. Now install ONE addon and (important) keep a log of what you installed, date and time etc. Then do what we like best and go flying - try to fly previously problem flights and see if you get CTD's. You may have to fly them a few times to be sure they are ok.If no CTD's, then install another addon and update your log. This is a long process, but it will pay off in the long run. At least it may give you an idea which addon may be causing CTD's and should be removed (test again after that).In my case, after uninstall/reinstall I had no CTD's. At least I know that hardware wasn't a problem. Then I started to install and test addons one at a time. Once again happily, no CTD's until I installed an aircraft which I like, but I got CTD's with it. I tested it many times at the same airport and others and proved that I only got CTD's with that plane.Anyway, it's a long process but for me it's worth being able to lessen or eliminate those pain in the tail CTD's.Good luck, hope this helps.