Terrible L4D2 performance on XPS M1710

[Sparrow_69]

My girlfriend recently inherited a Dell xps M1710 laptop from her brother. Specs are as follows: C2D T7400, 4gb ddr2 ram, 7950M GTX 512meg 179.67 drivers, 320gb 7200rpm, Win 7 N 64bit.

I recently installed L4D2 and have been watching the framerate with fraps. The performance is well, puzzling. No matter what the resolution or graphics settings (1920x1200 or 1280x720), all settings high or all settings low, the following always happens: Performance is generally good, 40-60fps, but the performance drops to near 0 for 1-2s. whenever I start shooting zombies. This makes playing the game quite difficult.

Since there doesn't seem to be much difference in framerate when changing graphics settings, I'm assuming I'm not being limited by the gpu. Is the cpu to blame? CPU does seem to running at 100% while gaming but I figured it should be able to handle the game just the same. Any ideas?

 

[Godmachine]

Do you notice it getting excessively hot when its running L4D2? Is the GPU fan kicked on at 100 percent? Nvidia is famous for having poorly cooled mobile GPUs and has seen more than a few recalls in the last few generations.

I would monitor the GPU/Memory clocks while gaming , see if they are being clocked down heavily. Could be a thermal issue.