If I were you I would send that p4 back.
If your on a low budget i'd get.
http://www.newegg.com/Product/Product.aspx?Item=N82E16813157115And one of these.
http://www.newegg.com/Product/ProductList.aspx?Submit=ENE&N=2000340343+4017+1050722265&name=Core+2+DuoAny C2D will make that p4 look like a commodore 64 in comparison.
Get 2 gigs of ram, and a copy of XP.
You can use an agp video card, or PCI-E.
Use all your old peripherals, and get a good 600watt power supply if you don't have one already.
You should be good for 3 years.
For a comparison.. I'm running this:
Asrock 4coreDual-VSTA motherboard
2gigs ram
C2D 6400
X850 pro AGP video card
600 watt power supply
1 western digital 80gb IDE ATA. hard drive
Windows XP Home SP2
I figure next summer/fall i Might have to upgrade the video card.
And I might switch to a SATA configuration.
Otherwise, right now i'm running the game with the hi res pack, and the detail slider maxed. Ground vis i set to half way.
Never have any stutters, and even in the DGS scenario with somewhere around a 100 fighter furball going on, everything ran smooth.
My old comp was a p4 3.2ghz sata config. and it's a snail compared to this thing.