Whenever I turn my PC on it's just noisy.
(My mom thinks it has something to do with the processor fan.
She doesn't even know anything about computer hardware and shit like that.)
And after 2-5 mins, the noise dies off.

its almost definately a fan
your mom is smarter than you think.

I think it has todo with a cable which is hitting a fan...happened to me...or just a older fan which needs to be renewed...

i agree with this statement. it could be the videocard fan or the cpu fan. It is NOT likely that a cable is hitting the fan. reason being the noise goes away after "2-5 mins" most computers have a boot cycle which incorporate running the fans at a higher speed for a certain amount of time (not sure why exactly, my guess is to try and remove dust from the heatsink) if the noise is however unusual and just recently started happening it could be due to an accumulation of dust into the heatsink causing your fans to run at a higher speed for longer to adequately cool your system down.

i would personally at that point take off the side panel and clean out my cpu cooler, and gpu cooler. however if your computer is under warranty you may not want to remove the side panel without making sure that it wont void your warranty.

If you bought your PC somewhat a long time ago or built a PC with a noisy fan, than that's likely it.

But it depends. What kind of sound are you hearing? It could also be a loss or poorly packed cable hitting the CPU fan.

Lol, your mom knows more about computer hardware than you, apparently. It's either the cpu fan, or gpu fan. Just open up the case and then turn it on. Clean it if it's dusty. Don't do anything stupid like jam something into the fan while it's running, or unplugging it and turning the computer on, etc.