"when the computer is turned on, a long noise is heard through speakers..it seems a long beep sound.. "
Since Windows has yet to load this sounds like one of those motherboards that routes the startup beep to the onboard sound card. To fix that you would ask the place that supplied the machine or parts. I can't begin to look into that since your post didn't give the detail needed or a link to your motherboard's manual. Hint? I go get the manual and see if a bios setting turns off the startup beep.
OS : microsoft XP professional
when the computer is turned on, a long noise is heard through speakers..it seems a long beep sound.. when i turned off mic on the volume control, the sound stops and that's when the time i can hear a playback sound..but i want to input mic through stereo phones... how can i do this..? also i have installed A4 TECH PC Camera H #2... can anyone help me?