i got a another problem with stereo mix. (win7)

hi. i'm new bigginer here. (this is not a gaming)

...
whatever my messy english. (don't get be angry)

i need help =<


i used-to record internet radio by using stereo sound.
(no need other sound.mic etc...
as you guys know...just needs

1.speker sound
( system sound also no need. u cud check mute in win7)
2.and stereo mix.
-during last 3 month it was very OK.


---- ---- ---- ----
but nowadays
i got a problem. (even i re-installed the win7 )
and used the same driver cd.(realtak ..for 32bit win7)

stereo mix problem
when u volume up,
there's howling+ noising up (it seems ... kind of my sound is repeating rapiddly)
more bigger bigger ...bigger.. god da--....

(if i control the sound smaller .. the sound gonna down at ..some sound point)
(some sound point, it's gonna bigger.and bigger .. and bigger ..again.!
that's not kind of white noise. real noise kind of echo =<


i've already taken off all the input sound but, (only stereo and speaker sound)
there's still kind of noise sound.

what should i do...? hardware problem?

i've tested 3 sample msi note book series(cx420) at MSI korea service center.
but there're also have a problem.* at some part.. sound's getting bigger bigger..
- clicking something that sound rappiddly repeated repeated more and more ......( =< )

please get me any idea for this.

help me.

have a good day everyone.

Go to the Volume Control Panel and check if anything else is playing.