I have an FX5500 and am not able to run FS2004 on it because it is one of the cards which microsoft does not support. I have spent Many hours trying to get it to work but there is simply no way to fix it. I have found at least three of four other people who have had the problem and have not ben able to fix it either.
I had a fx5700 which is basically an overclocked fx5500 and it ran fs9 fine
My current X850 was a MASSIVE leap from the fx5700 though (geforce 4mx420 to 5700 was small)