[vyverjet]

http://www.techsupportforum.com/f59/call-of-duty-4-lag-227987.html

I too am facing a similar problem of COD 4 getting stuck in between
I have a
1 gig ram
160 gig hdd
Pentium 4 processor
3 Ghz cpu
and an ATI Radeon X1550 256Mb graphic card.
This problem of cod 4 not running efficiently is very annoying

 

[McNinja]

Your system isn't fast enough, you should think about upgrading.

I would do the upgrade in this order

graphics card & PSU (first)
RAM Motherboard CPU (later)