what do i need ?  

You need an Intel Board and Processor that are latest on the market now for full durability from my experience and go for a DDR video card and maximize your ram. Get a 1TB hard disk. That stuff would make you machine powerful for gaming then

If you want to play the game, then, CPU you can choose AMD, at present, the market has reached four core. Graphics of course, high-clear. Display memory 1GB, there is a memory, the current board can support 8GB memory, on any game currently on the market are sufficient.
I wish you good luck.

get an latest graphic card so that u can play all the games with out any problem.

For a gaming PC machine, you might consider buying these hardware :

Processor -> a 3.0GHz+ Quad core or go w/ the latest Intel Core i7
Motherboard-> I highly recommend ASUS motherboard
GPU-> ATI HD4870
RAM-> Corsair OCZ (max of 24 gig on Core i7)

These are all the main hardware for you to have a very powerful gaming machine/PC.

Well it depends mainly on whether u already bought one on which u wish to upgrade or whether u plan to change completely to a new computer.
If it is the former u should try and buy the best graphic card that ur motherboard can support and also buy at least 4gb ram (DDR3 if motherboard supports it).
If u do these stuff its enough.Plus u also can format the current OS and reinstall to flush out all the viruses,trojans,etc.

If it is the later just google BEST GAMING RIG GUIDE.
Chose the one u find up to ur budget and buy it.Simple.

Or if u mean a software to get the maximum from ur current pc
Try overclocking the graphic card(using riva tuner).If u don't know how again google.
Plus go to this site and download and install the latest drivers.This is the best and safest way to improve the performance of ur computer- http://www.laptopvideo2go.com/

Thats all
Keep posting
APR

Hi christopher,
well for a good gaming rig,motherboard,processor ram and graphic card plays significant role.
Your motherboard depends on the type of your processor.
If you plan to buy Intel Core i7 processor, then go for ASUS P-series motherboard which supports Core i7.Well that's fastest motherboard available from ASUS in market and cost around 300-320 US$ in India.

Well prefer to buy ASUS motherboard because they are well built than Intel motherboards and are really faster and reliable and cheaper than the Intel.

Processor--
Best--Core i7(any edition)
Good--Core 2 Quad
Nice--Core 2 Extreme

RAM
4GB DDR3 1333MHz (OCZ or Corsair)
or 4GB or more DDR3 1600MHz (same brand)

Most imporatant---GRAPHIC CARD(totally depends on your budget)
BEST(Top end)--Nvidia GTX 295 Extreme 1.75GB DDR3 or ATI Radeon 4890 HD 1GB DDR5
Good(Top end)--Nvidia GTX 280 1.75GB DDR3,,, GTX 260 and GTX 230
Good(Top End)-ATI Radeon 4870 HD DDR5,,,4870 HD DDR3,, 4850 HD

NICE(most preferred if budget is restricted)(Mid End)--Nvidia 9800 GT 1GB DDR3 overclocked edition.
or 9600 GT 1GB DDR3
or ATI Radeon 4690 HD or 4670 HD 1GB DDR3.

Well for Graphic card, DDR3 memory is really good because it is faster than DDR2.

Then you'll be needing to buy all the latest stuff for your CPU. Latest sound cards, latest GPU, and including the latest processor as well. It might burn a hole in your pocket though.

If you need to buy a powerful gaming machine then i suggest you to opt for AMD Phenom. It gives you a great gaming experience. With this if you purchase a 9 series graphics card then the experience will be great.

your first need is a powerful processor. i recommend intel core i7 quad-core cpu.Then 2 things you need is RAM and Graphic Card i recoomend 4 gb ddr3 ram and 512mb/1 gb graphic card from nvidea gtx or ati raedon. Make sure your graphic card supports direct x 11. Then finally you need a 500-1024 GB HDD and an d a blu-ray drive

It depends. If you want everything, then get a very good CPU, a decent sound card, a big flat screen monitor, and the keyboard is up to you. But for the tower specifications, you need the top of the line graphics card, a decent bus speed, and a good enough amount of hard drive space (I'd recommend 300+ gig) and RAM (at least 4-6).