People are going to flame me saying this but I think a lot of it has to do with the code withing the game. Let's say we forgot how the game was coded...
1 - Could be your videocard drivers: run a driver cleaner and then install the latest drivers (the latest Nvidia drivers have great performance improvements for various cards though I'm not sure it applies to your GTS 240). Maybe try and test with no AA and lower resolution to see if it still occurs. If not, then it's simply a driver issue or processing power. You may meet the minimum requirements but these requirements weren't for people playing at 1080p.
2 - The game itself: Your best bet is to get the latest patch (if you have the STEAM version, just make sure it's auto-updating product is checked).
I called Dell and they said the maximum GPU I can put in the computer is an ATI 5770 which I thought was strange but a decent price at $145. I bought it and will see how it goes. I think my Aurora has an 875w PS so maybe all Dell had in stock was 5770's
I found compatible RAM for $70 compared with $234 from Dell. Seems Dell thinks Alienware RAM is special but this vendor guarantees compatibility. With my G15 keyboard I can see CPU and RAM resources and at rare times they both go up to 90% ie: downloading a new instance.
Funny thing, I ran the "Can my computer run this game" program on my newish work computer from the CoD: BO website and it rated the box a 9 out of 10. So I load the game up and it wont run worth crap on the lowest settings 800x600 with everything turned off. Its just a Dell Inspiron with an onboard GPU so I'm not surprised, just surprised that it passed the test with flying colors.
the thing is they sold him it as a gaming pc. they supplied him with a 1080p monitor knowing full well that the 240 is no better than a 9600gt which barley runs the game at 12/10 rez @60fps never mind 19/10... the rest of the system is fine. even with 3 gigs of ram. if your running a premium o.s. 64 bit then 3 gigs is perfect in tripple channel mode.
and yeah forget about buying your upgrades off dell they will rip you off.
the perfect card for your setup that gives great price to power is a 560ti or a 1gig 460gtx anything less than that and your not doing your i7 setup justice.
if you want to save a little power then get the ati equivilants. but you have the basis for a potentialy great mid to high end gaming pc.
Thank you again everyone. I didn't realize my screen's native resolution 1900 x 1200 was demanding. Shows you how ingorant I am.
So I got the 5770 because, as mentioned above, Dell said it was the best card for my system. The info on the card says 600w recommended, there's not alot of room in an Aurora, I wanted Dell behind me if I ran into troubles. The card is in and the game is running 1900x1200 4x AA, shadows, not sync'ing every frame. It runs fine but there are times when the game is choppy so i think, as others have said, its the coding in the game. I have no doubt my FPS is up but I dont know the command to put in the console to see it.
And thanks Hexit for the info about 3g ram in triple channel being fine as I was about to buy more ram. /salute
FYI: I just changed my videocard to a GTX 560 Ti and every once in a while I still get "jerks" while playing multiplayer (doesn't have to be when action heats up, it just does that randomly...though not very often). I think the game was simply a poor port. If you're getting low FPS, then like people above mentioned, turn down your AA and test with lower resolutions.