You don't mention whether it's a desktop or laptopk, but either one needs to be blown out with compressed air, at least annually.. If a desktop, take the cover off, then use compressed air to blow out all the dust from the power supply, the processor and heatsink, all the fans, and all vents in the machine.. Occasionally, the fans can start making excessive noise simply because they become caked with dust and must work harder to keep the dusty processor clean.. While you're inside the case, check to make sure all your fans are running.
If it's a laptop, blow out all the vents and take all covers off the computer to blow out the junk as best you possibly can.
Hope this helps.
My trusty XP home computer does it's far share of work and in it's 2 years has never missed a beat (unlike the previous ME computer I had), so I have lately been surprised by a mid-range annoying squeal coming from my computer. My once quiet computer now gives me a head-ache. I do all the usual maintainence to it (drive scan, Defrag,etc. - the antivirus runs automatically everyday but I have to manually set off the antispyware etc (I have AVG 8.0 paid version)which is no big deal.) The maintainence gets done regularly (other than the anti-virus) plus I'm always fully protected as I do things on the net. So I know it's alright there.
I'm just wondering what the squeal I hear is? I'm thinking it could be one of 2 things - the Hard Drive or the fan. I hope it's not the Hard Drive (WD 80 GIG - WD800BB), as the only times I've noticed it too be slow is when I have a fair bit saved on it (documents, pictures, etc). It happens after the computer has been on for a few hours or so & is louder sometimes than other times.
Does anyone know what this could be?