Computer fan keeps running

[Jinx]

I know this is potentially harmful for my computer, which is why I'd like some help. It runs quite often/basically all the time. I can have just one internet page up and the fan starts whirring like crazy. Is there any reason this is happening?

I recently had a trojan (McAfee said it was removed) and I'm currently running another scan on my computer.

[Night Fury]

It means there's a bomb in your computer.