The details are very lengthy but please read it completely.Just gave you all the information I know.

I have a Asus M2n-mx motherboard,Amd athlon X2 3800+.The motherboard is having a integrated Soundmax HD audio.The problem is that, I will lose the audio output just after 5 to 10min of booting my system.Ofcourse the time may vary.Its very random.If it doesn't work at all, I would have changed the chipset long back but it will work very fine some times.Once I loose the output, I should restart the system to get it back.Some times it says that "no soundmax hd audio is present".

I was very frustrated and I bought a Soundblaster sound card.This worked fine for 1 year but stopped working immediately after the warranty period is finished. So again I tried if my old integrated audio is working.I installed the audio drivers and it worked flawlessly for nearly 3 months. I don't know why. Again the same problem started. I tried removing the Hardware acceleration but no use.I tried all the hotfixes from Microsoft but in vain.

There is no specific program which makes it stop working.It may stop when listening music or playing game or watching a movie.Its the same for Vista.I will get a disturbance in my headphones or speakers just a second before its going to stop.I don't know how it worked without any problem for 3 months.Please any one figure out the problem.

Since you're getting the "No soundmax HD audio is present" message (doesn't show up in device manager?), I think the following possibilities are probably eliminated, but it wouldn't hurt to verify:
1. Damaged audio extension/speaker/headphone cable, e.g. broken conductor works intermittently depending on physical orientation of cable.
2. Damaged speaker jack.
3. Something plugged into any existing front jack, which normally may disable the rear jack.
4. Bad headphones/speakers.
5. Foreign matter in/on jacks, board, or audio chip connections.
6. Driver problem.
7. Conflict with another device.

The problem is more likely a bad motherboard or audio chip.

You could also try, with the computer disconnected from power, some electronics/flux cleaner around the area of the audio chip on both sides of the board. The application notes for the Analog Devices AD1986A chip your board uses also details in several pages how small changes in the values of supporting electrical components and temperature can cause the chip to perform out of spec.

The fact that the Soundblaster also failed seems somewhat suspicious, but I'd probably slap a new motherboard (maybe different brand/model) into the machine and if the problem persisted then begin pulling my hair out trying to isolate the cause.

Same problem; mechanical error is unlikely as many other people have the same issue. Soundmax is REALLY user-unfriendly. The same issue occurs for me whenever I switched the stereo jack with a headphone jack (the green one) (I only wear headphones when playing computer games).

I got it to work once after I reinstalled the driver but it happened again once I plugged in the stereo then headphones. Hope that helps narrow your search.