I recently bought a new computer with an Nvidia 8800GTX, and the first game I installed was F.E.A.R. I performed the Stress Test and my FPS was almost always over 100FPS. Now when I perform the Stress Test, my FPS is, at the most 50 FPS. When I was getting 100 FPS, I had all of the settings to maximum and I had 43 programs running in Windows Task Mananger. Now I have 33 programs running and I am getting half the performance. Also, at times the FPS gets very slow, down to sometimes 19 FPS and this never happend before. Does anyone know why this might be?

Defragment your HDD. Run Virus and spyware scans.

What power supply do you have. A weak one thats dieng could lower performance.

I ran virus scans, I am 99.0% sure that I do not have a virus in my computer. I have uninstalled unecessary programs, cleaned my hard drives, defragmented my hard drives, I have taken away the majority of my Owner start up programs in the msconfig toolbox and error-checked my computer. I have a 700W FSP PSU and a 300W FSP Auxliary PSU.

System Specifications:

-Intel Core 2 Duo E6700
-Nvidia 8800GTX
-ASUS P5N32-SLI SE Deluxe Motherboard
-2GB's of Viking RAM
-1x 300GB WD C SATA HD
-1x 160GB WD R SATA HD

-I have 87% free space on my 160GB (main) drive, and 99% free space on my 300GB drive.
-Give or take a few, I have 31 processes running in the Task Manager.

-In F.E.A.R. with all settings on maximum, I get 15 FPS at the lowest and 59 FPS at the highest.
-I used to get over 100 FPS more than 50% of the time with all settings on maximum.