Hi and welcome to TSGF this could be from either your hardrive or possibly a fan,you would need to post more info ie could you pinpoint the place you heard the sound ie near the front of the computer or from the rear or side,also you should update to sp2,after we see if we can find your issue,if it came from the front it is likely the hdd so back up your data as it may fail,take the side off and boot it up and see if it repeats the issue then you may be able to pinpoint where the sound is coming from |