Crysis audio problem in windows 7

This is a very lengthy text,please read is thoroughly..

My problem is, whenever i play crysis 1 or crysis warhead, the sound gets slower then the game(display). I here the sound as if everything is happening in a tunnel or a cave. I mean its like reverb, that too very slow....but it doesn't happen while playing songs or videos.
it never happened when i played this game on windows xp. Other game like COD Black Ops runs a bit slower than it ran on Xp, and sometimes, that crysis sound problem comes in this game too. But in a lesser amount (for 1 or 2 seconds)....
The other games like NFS Hot Persuit and Devil May Cry 4 runs smoothly with no sound issues....

One more thing, for sometime in some levels the sound is ok in crysis & warhead. But in some action scenes and sometimes for no reasons the sounds starts cracking and gets slow....
I tried reducing the visual and audio effects to LOW form game's advanced settings. but saw no improvement. Whenever i install realtek audio driver for windows 7, the sound gets worse and i can here distortion on playing songs and videos also.
I also tried changing the audio frequency from control panel>sound>playback devices.....
But no joy.

I think it may be because of
1>installing windows updates
2>i installed directx 9.0c after installing windows 7 coz i didn't knew windows 7 has pre installed directx 11. May be my directx installation overwrited some directx 11 files.
3>when i tried installing windows 7 from booting, it said that the drivers are not found.
so i installed it from windows xp, from my computer. the message didn't came and it was a clean installation. i saw the the drivers are properly installed. I removed windows xp files from windows.old.
But nw after shuting down the lights of my computer don't turn off. i have to manualy do it by pressing the CPU button for some time. IS IT GOOD??
PLEASE HELP.....FOR BOTH THE PROBLEMS( sound & lights)

More Details
RAM: 3GB
PROCESSOR: INTEL DUAL CORE 2.00 GHz
OS: WINDOWS 7 ULTIMATE 32BIT
GPU: ATI SAPPHIRE HD 5670 1GB
MOBO: ASUS P5SD2-VM

well,as for your sound problem,you may want to look into getting a dedicated sound card and as for installing dx9,windows 7 can have dx9,10,11 installed all at the same time,so no problem there,but some things to try...make sure that stereo is selected in sound speaker properties,make sure you dont have any kind of reverb selected in sound properties and make sure that the speaker connections are not reversed.......

roll back your sound drivers to a previous version.

http://dlcdnet.asus.com/pub/ASUS/misc/audio/Realtek_Audio_V6015473_vista.zip

try out this...download the file,
[1] then go to my computer>properties>device manager.
[2] then right click your present audio driver and select 'update driver software'
[3] select browse my computer fo driver software
[4] then choose 'Realtek_Audio_V6015473_vista\Audio\driver\Vista'. Vista64 for 64-bit

system should install these drivers. If it does u should have no more problems.

NOTE: this is for windows 7, don't knw if wll work on Vista

Sounds like performance issue to me. Had the same problem with NASCAR 2003. Sound would echo and reverb or something like what your describing. I turned the Hardware acceleration off and that fixed it. Windows 7 does not support this feature. I recommend playing with the compatibility options. For WinXP etc., see if that clears it up. Also be sure you select run as administrator.