Call Of Duty 4 Jumpy/Glitching

I got Call of Duty 4 yesterday for my computer. I installed it and I am running at the default settings at a resolution of 1024x768. Why does it get really jumpy anytime there is an explosion, lots of gunfire or airstrikes being called in? As long as there isn't a ton of stuff going on, it is fine. This only happens when everything gets pretty crazy and that's when I need it to stay smooth the most. Also, it is worse in multi-player online play than it is in single player offline play. Here is my PC configuration:

Quad Core Q6600 2.4 GHz Processor
BFG 8800GTX OC 768 MB RAM Video Card
4 GB Corsair PC6400 5-5-5-18 RAM
XFX nForce 680i LT Motherboard
Windows XP Professional SP2

Any ideas? I have never had any trouble with a game getting jumpy. I bought Frontlines Fuel of War and played it for 10 straights hours on 1680x1050 resolution and didn't have a bit of trouble. I am getting kind of frustrated because I know my computer is more than capable of running this game.

Thanks in advance.

Yea, it is pretty frustrating. I have never had any trouble out of the video card running a game. I think some of it might be lag in the internet connection as a lot of people complain about that, but the jittery screen when things explode has me puzzled. I have the latest drivers for everything as far as I can tell.

How do I go about enabling Vsync?

Also, my screen only refreshes at 59 MHz or 60 MHz...which do I want or does it really matter?

Could any of the hardware other than the video card be bottlenecking the system? I have a single 400 GB SATA hard drive and I was wondering if it could be glitching due to reading information from the hard drive. Would I notice any difference if I got two of the new 10K RPM Velociraptors and put them in a Raid configuration?

theres vsync on the options in cod4, its called vertical sync. 1fps per hz for monitor.