Games NFS undercover, Left 4 Dead run really laggy choppy audio

[Shifat]

help! i just bought a new pc and it seems like whenever i try to run a game i.e.: NFS undercover or Underground2 or left4dead my computer slows down a lot and the audio starts crackling.

the games run really smoothly for 2 seconds and then start lagging for 5 seconds and then goes back to normal for a bit and then goes back to laggy and it gets really frustrating! lol

although sometimes they run perfectly i have no idea why the games lag like that even after i turn the game off the audio will still be choppy and make crackling noises i have nothing running in the background either.

all the problems go away after i reboot though, but then they come back >:I

PC specs:
intel core2quad Q8200 @ 2.33ghz (not OCd)
8gb ram ddr3
ati radeon hd 4650
1TB hard drive
Vista 64 bit (waiting for windows 7 to ship =p)

please help me!!!

 

[AndrestheBean]

how big is your monitor?

 

[Shifat]

its a 22" flat panel

 

[LinkedKube]

Your cpu has a low amount of L2cache, which is helpful in games. Its the more expensive part of cpu manufacturing. The cpu isnt that powerful in short, although a quad core. Your video card, is sub par as well. I wouldnt game on a monitor larger than 19" with that card, I think that's why Andre asked you what size monitor you have.

 

[Shifat]

ahah i see... so i should get a new cpu? i already ordered a gtx250 yesterday and reading stuff about sli i might get another gtx 250 and actually set it up in sli.

maybe that'll help?

 

[AndrestheBean]

you only benefit from sli if you have a large monitor, you should just get a better single card setup, like a gtx 275, it can handle all games at your resolution with no problem.