I BUILT MY SON A NEW PC A FEW WEEKS AGO IT WORKS FINE BUT CERTAIN GAMES HE CANT PLAY AND I THINK ITS THE ONBOARD GRAPHICS CARD NOT POWERFULL ENOUGH ANYWAY I BOUGHT A NEW GRAPHICS CARD BUT WHEN I PUT IT IN MY SONS PC NOTHING HAPPENS IT DONT REGISTER ITS AS IF ITS NOT THERE I GO INTO DEVICE MANAGER AND ITS NOT THERE ONLY ONBOARD CARD IS THERE I PRESS ADD NEW HARDWARE AND IT STILL DONT PICK IT UP.THE FAN ON THE CARD WORKS BUT NOTHING ELSE EVEN WHEN I PLUG IN MONITER NOTHING..I KNOW THE CARD WORKS BECAUSE WHEN I PUT IT IN MY OLD PC AND TURN IT ON IT INSTALL THE CARD AND IT WORKS FINE. I READ SOMEWHERE TO GO INTO BIOS AND DISABLE ONBOARD GRAPHICS CARD BUT THERE IS NO OPTION TO DISABLE CARD ANYWHERE IN THE BIOS.PLEASE HELP AS I HAVENT A CLUE. PS THE COMPUTER SPECS ARE AS FOLLOWS.INTEL PENTIUM 4 PROCESSOR (1999 MHZ).SYSTEM MODEL D845GRG.(BIOS VERSION AND DATE INTEL CORP RG84510A.86A0028.P15.0302260937-.26.02.2003)SM BIOS 2.3) TOTAL PHYSICAL MEMORY 1.280.00 MB- TOTAL VIRTUAL MEMORY 2.00 GB- AVAILABLE MEMORY 1.96 GB.-ONBOARD PLUG AND PLAY MONITER.INTEL®82845G/GL/GE/PE/GV GRAPHICS (OS XP PRO.VERSION-5.1.2600 SERVICE PACK 3 BUILD 2600)SYSTEM MANUFACTURER INTEL)400W POWER SUPPLY-. THE CARD IM TRYING TO INSTALL IS ATI RADEON 9200.256 MB AGP 3D VIDEO CARD TV-OUT VGA DVI. THANKS ANY INFO WOULD REALLY HELP AS THIS IS MY FIRST BUILD THANKS LOOK FORWARD TO REPLY

Argh, my ears!
Please don't type in all capital letters, it looks as if you're shouting.

Those are old components now, who sold you them as being new? The board has a 2003 date on it.
What games is your son trying to play?

First sorry about writeing in big letters its easyer to see.the games are(farcry)need for speed carbon)simpsons hit and run)call of duty 2)when you say the board is old do you mean the motherboard or graphics board im new to all this stuff.wasted youth lol.thanks

With all due respect, the board has a date of 2003 on it, I very much doubt it will be capable of Far Cry, and that graphics card is old too.
You state in your original post "I BOUGHT A NEW GRAPHICS CARD", then proceed to list a card that's been out of production for about five years.

Realistically this computer isn't capable of modern day gaming and it sounds like it can't talk to that card either. There's not a lot you can do about this unfortunately, and it's not worth replacing the board for one that can talk to it, you may as well replace the computer.

Thanks for advice.i bought them off ebay as used but the guy i bought it off said it was a year old.it cost me £40 for motherboard and processer and £20 for graphics card.he seen me coming lol.could you please suggest a cpu and motherboard thats good but not too expensive and graphics card thanks for your time gelmancadet

Sure mate, what sort of budget are you looking at for this build?

What parts of the computer do you need and what do you already have? (i.e. don't forget monitor, keyboard, mouse, speakers, OS, etc)