Lag Mania

Hello,
 Not really assistance on 'playing' the game as my mate is helping me out on that front and I'm picking it up.  However, I run a very similar rig to his (he has 4gig ddr2 ram and I only have 1gig ddr - he has 5.1soundcard/headset & 16mb broadband compared to my 8mb) But here's my spec.

Processor : AMD Phenom 9500 Quad-Core
Memory    : 1Gig DDR2 Ram
HardDrive : 250gig Sata HD
Graphics   : Nvidia 8600gt
Internet    : 8mb

 As stated the only difference between my rig & his is 3gig ddr2 ram. His internet is 16mb aswell (but he plays  at the same time as his partner). Yet whenever I'm indoors I have crazy lag. Outdoors its seemless on any settings the moment I go inside even on minimum settings. I find this very odd as I have heard of people running it great on rigs with 1gig of memory & on 8mb internet. I play Call of Duty 4 aswell with 150fps so I am confused why I get this lag.

 Any advise would be greatly appreciated, all I run in the background is Ventrilo & Xfire. Please help, its annoying me

I put that fix in my useroptions file, ran the game & ran indoors, worked great. Booted up a mission & went indoors & lag was the same as usual :S Is their any other fix? Or a set useroptions/config file?

// Resolved - Deleted my original useroptions file & created a new one, tested outside of mission & inside & when into the chinese areas (more detail) and still no issues.

Thanks,
IDraVen

hmm, i tried the fix, it helps a little but the lags not gone, its still rather bad >_< help?