Help with a new build

You are going to be very hard pressed to meet this budget.....

Add $200 to it, and, then you will be able to afford some memory (at least 4 gb worth) and an OS for what will likely be an AMD X2 or X3 based cpu ($70-$100) and a mid-range video card ($150; gaming at 1920x1080 is not like running a QUake3 system!) and a 750GB hard drive ($30), and a case with 600 watt PS ($80)

I believe THG runs $500-$750 barebones gaming system guides occasionally.....

Agreed that $400 will be rough... Do you have a Microcenter near you?

To save on expenses would I be able to use my Hard Drive from my Dell? And use Windows XP as my OS?

http://www.tomshardware.com/reviews/build-a-pc-overcloc...

Listed above is THG for $500 systems; for gaming, not the GTX460, not expensive today, and, by far the most important part for a gaming system. (80% of it's frame rate is a result of a decent GPU!) I concur 100% with their recommendations!

Most likely you could use your older IDE hard drive/CD ROM/DVDROM drives, but, if I am not mistaken, the latest Direct X 10/11 was never even available for WinXP? (I love WinXP too, am sorry to see it go on my next build as well.....)

I've not priced Win7 OEM versions yet.....