General

High Pitch Screeching Sound coming from Laptop

A few weeks ago my dad somehow managed to save my hard-drive from going kaplooey.
Ever since then my laptop has been completely fine. But now, it sometimes emits a high-pitched screeching noise that at times isn't even noticeable.
It isn't too much of a problem to my ears yet since sometimes it isn't as annoying and sometimes it doesn't even make the noise, but I'm just wondering how can I fix it and why is my laptop doing this? Is it a sign my hard-drive is going to go again?
I'm going to backup my files on an external hard-drive just in case.
Any help is much appreciated!