Issues- Suggestions?

I really don't know how to explain this to everyone so I will state as much as possible.

About 5 days ago my computer, as I worked, started to rev up suddenly once about every half an hour or so. At first I didn't notice it, but for the last two nights I was left my computer on, something I don't do very often, and about every half an hour it would rev up suddenly. Today it has stated doing in about every 10 to 15 minutes and lasting about 10 to 15 seconds.

I first though GPU but fan speed is at 55% and no game or program is running. I check SpeedFan and it gave me the following readings at idle:

CPU: -51F
Internal Temp: 100F
Temp3: 132F
Temp4: 108F
Temp: 32F
Temp: 32F
Core0: 118F
Core1: 115F
Core2: 118F
Core3: 115F
Fan1: 775 RPM
Fan2: 0 RPM
Fan3: 0 RPM
Fan4: 765 RPM

This is about the same at rev ups, at times, (not often) everything but the CPU would peek at around 120F. CPU would stay about the same temp. Anything above 120 would not change.

Does any have an idea what the cause could be? I cleaned out about 2 weeks ago and ran antivirus/spyware this morning with nothing out of the ordinary.

Any help would be appreciated.

Cheers,
Adam