Check all the screws that hold the fans to the case or the CPU cooler.
It could be dust in the fan's bearings.
It could be a bearing going bad.
It could be a fan blade that has a nick in it.
To test if it's the vid card fan...IF you have a modern Intel CPU, you can run your monitor from the connector on the motherboard and take the vid card out.
Btw, the computer itself is called a desktop or a tower. The "CPU" is just a chip on the motherboard.
You can also find exactly which fan is the problem, with an 18" piece of wooden dowel rod.
With the computer running, put one end of the dowel rod in your ear (gently) and touch the other end to a part of the chassis nearest to the fan you want to test.
The wooden dowel rod acts like a stethoscope.
DO NOT put the end of the dowel rod into a moving fan blade.
Also, give us a Speccy screenshot please...
Get SPECCY here: http://www.piriform.com/speccy/download ...get the
FREE version from the:
Piriform Link ...Speccy is a really nice system hardware/temperature, information Utility.
...simply install it...and run the program...then post a screen shot of the main page of the program, when posting a problem/question on these forums.