Constant crashing

[orde02]

My system is a little old now, but while I'm waiting for my new rig, I'm stuck with this one.

Intel Quad CPU Q8200 2.33GHz
Windows XP Home Edition
Nvidia Geforce GTX 280 1 Gig
2 Gig ram
Creative Sound Blaster X-Fi Audio
DirectX 9.0c

CoD actually runs fine on my rig with most settings set to medium. My problem is that it crashes on most missions, particularly anywhere near land. Over the sea isn't so bad but I can't even attempt a take off from an airfield. Also, switching from cockpit to external views is a killer too.
From reading other posts, I get the feeling it's running on XP that's the main problem, but can anyone offer any other advice?

Thanks