Can bad RAM cause really low FPS?

I'm wondering if dodgy or slow RAM can cause a decent spec computer to run slow?My problem is this. My system is as follows:Intel P4 3.2 o/clocked to 3.6 GHzATI Radeon X800XT Platinum Edition1GB RAM (DDr, but unsure of actual speed)I've got a decent power unit bought specifically to handle all the power demands (I think its 600W).My PS are in the high single numbers (about 7-10 fps) in the following situation:PMDG 747 inside cockpitAt Heathrow (standard FS scenery), Dense scenery, Sparse Autogen.AI set to 75% with MyTraffic 2004. With mipmap detail and world texture set to medium settings.I was expecting better FP from this system. Should I be? And if I should, wheres the weak link thats causing such low FPS?Thanks for any help.-Phil