My case fan all of a sudden got really loud!

[BlackScarlet]

It just started rattling and grinding and sounding terrible. It's the case fan on the back, not the side, not the power supply or the psu, I know this because I reached in and put my finger in the fan on the back, stopping it, and it was what was causing the noise.
It was so loud that I actually inhibited the fan so it's not working now. My case is open so I figured it wouldn't get too hot in there, but what can I do to fix the fan?
Blowing it out with an air can didn't do any good.

 

[mailpup]

The bearings might be failing. It happens. You just replace the fan with a new one. It's easy and new case fans don't cost too much.