"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.