Computer fan speed just went insane!! Freaking out here...

[Goldom]

So I cleaned out inside of computer today.. just taking out dust and all, normal stuff, and I just noticed now that MBM is showing my fan at over 8000 RPM.. I have never seen it above maybe 5500 before. I actually am not sure which fan it is that has the sensor on it, though I would assume the CPU.. I'm thinking it must be something wrong with the sensor cause I would be hearing a difference if it was that much faster, wouldn't I? And no, it's not that the dust in it was slowing it down before, I've cleaned it tons of times and it's never shown being this fast... I'm afraid it's going to break if it's really suddenly sped up so much.

(Update: I opened it again, found a totally unrelated massive cache of dust stuck to the HD, tried unsucessfully to take the CPU fan off to look at it, turned the system back on, and fan is now at a calm 4300 RPM. I have no idea. On another note, how the @#%^ do you get the fan off the cpu?! I realize it's different for everyone, but I opened two white bars vertically on the side, then released 4 press latches, two on the top and bottom, and the stupid thing just won't come off still.. it almost look like the whole thing is being held in with a solid plastic brace, though if it isn't able to come off short of removing the whole cpu, why would it have all those other clips at all...)