There you go it's your graphics card which is not good, try putting in 512MB ATI Radeon 4850. Yes, fs 2004 is compatible with vista, i have both versions of of flight sim, works perfect without any trouble. Also your cpu is not that great try getting a quad core or intel core 2 duo (which one i don't know) get the clock speed like 2.6GHZ or higher. There is nothing wrong with your ram,hard drive, operating system.