Problems with a Dimension 8400

Hi,

 

I just recently bought a Dimension 8400.  It's also a Refurb.  Got a P4 3.2 ,2 Gig of DDR2, and Nvidia Geforce 6800.  I am very unpleased with the performance of the system.  I am getting terrible frame rates when playing games such as Call of Duty United Offensive.  I have tried several things such as re-formatting and re-loading Windows XP and also using latest drivers from Nvidia and drivers for my Sound Blaster Audigy 2ZS.  With the resolution on 1280 x 1024, Details on High/Normal, Bilinnear, and Vsync off my frame rates dip down into the 30's and 20's.  It happens most of the times on maps like Foy and Cassino.  I also noticed that it seems to dip down very low when there is very intense mortar fire and shooting.  Leading me to believe that maybe the problems may be sound related.  The machine never really hangs up and the sound doesn't sputter but it's just very annoying that the frame rates are dropping down so low that the game is virtually unplayable.  Also changing the resolution doesn't seem to help things out as far as the frame rates.  I have noticed from the very beginning that this system seems to be on the slow side even just within windows as far as delays when buttons and windows are clicked and screen re-freshes.  I'm starting to think that there is a problem with the processor or something and it may not be performing up to par.  The reson that I think it's got to be CPU related is that I tried also using a GeForce 6800 Ultra card in the system and got similar results in playing the game.  There is a bottleneck somewhere and I've been racking my brain trying to figure out what might be wrong with this system.  I was wondering if anybody has had similar problems.

 

Thanks