PLEASE HELP!!!

PLEASE HELP ME.
If anyone can help it would get rid of my massive headache at my dumb computer.
I have a custom built computer that i got last year that has a bad sound problem. When playing games, only games, there is a horrible static-screeching-crackling that comes out. I have tried differenct speakers ( no help) headphones (no help) bought a new soundcard X-fi Fitality ( didnt help) switched out graphics card with no help either. I have updated the drivers for both graphics and sound card. I just dont know what to do. I had a guy who build gaming pc's look at it for 2 hours and he was stumped. The strange thing is not all games do it. Call of Duty 4 and Crysis are the worst. The other strange thing is that it depends on the map and where is am on Cod 4. On Creek for intsance i will be outside with crackling distorted sound and when i go in the cave it clears up and is perfect. The guys at Geek Squad said the last thing i could try would be buying a new motherboard which wouldnt be horrible because i would like to get SLI but what if that doesnt help it either. Any ideas please let me know.

Odd.... who built it? Who ever built it should provide the tech support.

Dual core 3.00GHZ
XFX Nvidia Geforce 8800gt XXX
3Gb of ram
250gb Hardrive
Windows XP
Biostar Motherboard
X-fi fitality sound card

Could be wrong here but,,,it seems that you have either a driver conflict or a software problem..
So the first thing that you must do is establish that all the files on the affected hdd/partition are A OK,i usually use a windoze ME boot disk with scandisk,or,,you can put your hdd in another XP system use cable select if it is a pata,if serial just install as 2nd hdd,system should boot from 1st hdd,then use right click on the partition/hdd in question select properties,select tools,and under error checking ,select check the volume for errors,you could also do the second selection which will examine the hdd for surface errors,takes forever,you must be certain that there are NO SOFTWARE errors,cross links etc,on the hdd in question,also two other items that might be of interest are the condition of the swapfile and,the last time the hdd was defragged..
And finally as a last resort you can reinstall XP right over existing install,,but it should be the exact same as installed,otherwise it will come up as a new install..
OTOH ,,you could just say "fugh it all",, and get that sli mobo.
Seems almost certain that you have a software problem,also you might reinstall your DirectX...

As i've been saying for some time, Creative cards do this on certain games on certain motherboards. I've seen this happen on anything made by Crytec and Far Cry 2 so far. This is on XP, BTW.

EDIT

I'll try CoD with my X-fi later to see if that game has issues; i've been playing on my onboard sound for a few months now until Creative comes up with some decent drivers...

Hello guys thanks for your posts.
Ok when i got the computer that sound problem was there with the onboard sound. I called him and told him about it and he sent me a junky plain old 5.1 sound card. Same problem with those also. When i got the computer it had a 450 W power supply that i sold to get a new 650 W which didnt help any. I have tried 3 different graphics cards ATI Radeion 9250 MSI 8600gs and i am using my 8800gt XXX now. I even sent the computer back to the maker in california ( i had to pay 100$ back and fourth) he said he never heard static which is a lie becuase geek squad and another computer maker i talked to heard it. Now for the drivers i updated all the ones that i thought would be important graphics card-sound card-dirext x-updated newest patches for the games. I dont want to spend money on getting vista and i really like xp but i havnt tried that. This problem is so strange and frusterating. My games run great on highest setting exept crysis but its no fun with such bad sound you cant understand what the guy on cod 4 is saying when you start a match. Any more info you need just ask.

Already have done fresh install of XP.

lol yeah.
I think i will get an Asus. They have really good ratings.

650 w i dont know the brand though. its not that though because i have already tried another one.