alot of ppl suggest builds that they have no experience with or dont even own! research what ppl recomend !
the build i suggest is what i use and its great, i havent had a probelm yet ! and later down the road if you wish to overclock you can
here is some more links to help you choose
Antec Solution SLK3000-B Black Steel ATX Mid Tower Computer Case - Retail 45.00
Computer cases are a personal choice you can choose what you like i choose this one cuase its simple and from a good company antec i dont like cases with 50 pink neon lights and a screaming yellow case

and with the money you save on a simple case you can put it toward a better graphics card, processor, porn, 40 ounces etc etc !
ENERMAX EG425P-VE SFMA 2.0 ATX12V 420W Power Supply - Retail 76.00
YOU NEED A GOOD POWERSUPPLY DO NOT BUY ONE THAT COMES WITH A CASE I CANNOT STRESS THAT ENOUGH !
for new motherboards you also need a 24 pin power connector this enermax noisetaker is quit and has a 24 pin power connector and enough amps to power anything you throw at it !
AMD Athlon 64 3200+ Winchester 512KB L2 Cache Socket 939 Processor - Retail 190.00
great processor the wincester cores are easily overclockable and do not heat as much as there intel conterparts also the best processor for gaming ! also way cheaper then intel here is a review of what this processor can do in halflife 2 compared to other intel chips (also this pattern is the same with most if not all videogames)
http://www.anandtech.com/cpuchipsets/showdoc.aspx?i=2330
CHAINTECH VNF4/Ultra Socket 939 NVIDIA nForce4 Ultra ATX AMD Motherboard - Retail 84.00
at first i was skeptical about the chaintech brand motherboard but after i started hearing good reviews and ppl recomended it i decided to give it a try and i love it ! i had no probelms setting it up ( it was plug and play for me) and no stabilty issues also its a great overclocker ! here are some reviews
http://www.ninjalane.com/display.aspx?docname=vnf4ultra
http://www.neoseeker.com/Articles/Hardware/Reviews/vnf4ultra/
CORSAIR ValueSelect 1GB (2 x 512MB) DDR 400 (PC 3200) - Retail 82.55
ram is ram alot of ppl will argue you need low latency overclocking ram that costs over 300 bucks that is not nessesary its nice but not worth it money wise you can run a divider and get good results ! AMD 64 processors are not as ram reliant as INTEL processors for overclocking
Seagate Barracuda 7200.7 SATA NCQ ST380017AS 80GB 7200 RPM Hard Drive - OEM 68.00
Serial ata is the way to go ! also new NCQ technogly even make it faster along with seagates 5 year warrenty this drive is a steal !
NEC ND-3520A Black IDE DVD Burner - OEM 48.99
BEST DVD BURNER I HAVE EVER USED ! 50 bucks

nuff said
eVGA Geforce 6800GT 256MB GDDR3 PCI-Express x16 Video Card - Retail 359.00
im a nvidia fan boy and i love the nvidia drivers this is a great card and will be great for gaming for a good 3 years and can easily be overclocked to ultra levels ! now the x800xl is also a great card and is around 250 -299 bucks which is great too and preforms almost as good as the 6800gt ! but does not have model 3.0 either card is good for gaming
here is a review of the 6800gt and the x800xl going head to head
http://www.anandtech.com/video/showdoc.aspx?i=2299
now if you really dont wanna spend that much you can get a 6600gt for about 179.00 it will play all the newest games but dosent have the longevity like the 6800 or ati x800xl
the 6600gt is 128 bit and 128 mb ram while the others are 256 bit and 256 mb ram
Total 953.54 (with the 6800gt) Total 879.53 (with the x800xl)
now this is what i use and i love it but i cant guarentee you will, just use this as a outline and build a comp that for you !
remember
AMD socket 939 processor
Motherboard with NVIDIA nForce4 Ultra chipset socket 939
A GOOD POWERSUPPLY ! Antec, Enermax and Forton are some of the good brands! make sure it has 24 pins !
stick to those and everything else should be fine !