I keep trying to run COD4 at optimal settings and it keeps lagging and the fps sucks

what settings should I set it at for good gameplay/graphics?

Version 6.0.6000 Build 6000
System Manufacturer HP-Pavilion
System Model GC673AA-ABA m8100n
System Type X86-based PC
Processor AMD Athlon(tm) 64 X2 Dual Core Processor 5600+, 2800 Mhz, 2 Core(s), 2 Logical Processor(s)
BIOS Version/Date Phoenix Technologies, LTD 5.09, 5/3/2007
SMBIOS Version 2.4
Total Physical Memory 2,941.88 MB
Available Physical Memory 1.49 GB
Total Virtual Memory 5.93 GB
Available Virtual Memory 4.30 GB
Page File Space 3.17 GB