The computer I am using is a: Lenovo 3000 J105 Series desktop. 1.8GHZ AMD Sempron 3000+ 1GB RAM Windows XP. The humming goes away after like a few seconds. I think it might be my power supply unit. SInce this is a Stock 6 year old system my computer's CPU has a fan + Heatsink on it. The task i usually do is surf the net run Yahoo! instant messenger and play videos. Also having my anti-virus [avast!] And [malwarebytes anti-malware programs. protecting my system. Could itquite possibly be my Powersupply needing cleaning? It has dust on it.
Crack the case and carefully vaccum out the larger dust and lint debris - a small brush can help with this.
Then take it outside and used a canned air duster (or a air compressor), using short bursts of air to blast the dust out, particulary out of the power supply (blast from the inside of the chassis to outside), the heatsink and any other cooling fans.
If you use canned air, don't tip the can - you want the gas, not the liquid to come out of the can.
Don't forget to clean the front of the desktop as air comes in from the front on most desktops and can accumulate large "dust bunnies".
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