Well, noone in hardware seems to care.
It might not be that they don't care but don't know the answer. CFS1 is getting on now & most people are running CFS3 or FS9 on powerful machines & WinXP. Not much point in commenting if you can't help. You seem to know what you're talking about & probably know more about this sort of thing than me. I've had CFS1 since it was first released & it always ran fine on the lowest-end systems. I seem to remember some people with a Celeron CPU having problems. You have plenty of RAM & it sounds to me more like a conflict of some sort.
Here's a few tips from my failing memory. First, I don't think DX9 is the problem. I installed the latest DX9.0b recently & CFS1 runs fine. Check your Windows desktop display settings. CFS1 never liked running above High Color (16 bit).
Install the No-CD patch or tweak Combatfs.exe as shown in the Help section here. This removes the CD & CD-ROM drive from the equation completely.
If you're not running CFS1 in Full Screen mode, hit Alt + Enter.
If you know how, set up a proper Windows Swap file. Windows does not manage virtual memory efficiently. Then defrag your system. This & more tips here.
http://www.burzurq.com/forum/trevtweak.htmlPlease tell me if any of this helps.