Computer slow despite having excellent hardware

I prefer to work through a problem backwards so if you're just here for a solution start here. If you want to see the process, continue reading.

Resolution

In the end the problem ended up being that my CPU was un-clocking itself to protected against overheating. The reason for this was due to the fact that there was a thick layer of dust between my CPU fan and heat-sink. After buying a can of compressed air and fully clearing out the heat-sink and case of any dust and debree my Maximum Frequency was back up to 100% (actually 104%).

The Story

Over the last few weeks I had been fighting a losing battle with my computers performance. Recently having upgraded my Windows 7 installation to Windows 8 I started noting that flash based video play back was sluggish and would cause the rest of my tasks to feel delayed. Jumping to the obvious conclusion that Windows 8 was the problem I decided to re-install Windows 7 and get my PC back to where it was previously. Much to my annoyance and surprise the problem persisted even on Windows 7. My computer at this time is no slouch and contains the following specs

• Intel Core i7
• 24 GB of ram - triple channeled
• 2 Videos Cards - Nvidia GeForce GTX 570 & Geforce 275
• SSD Drive for C:

Identifying the problem

Trying to figure out the problem was difficult. I was pretty sure it was hardware related but couldn't understand why the symptoms would only appear to show when playing video. Again jumping to conclusions I assumed it was a video card issue or driver issue. Then one day I finally pushed my computer to the limit and it just shut off  and started giving me bios error messages about  overclocking and would fail to reboot. This all seemed strange because I'm not overclocking my CPU and generally my CPU runs at around less than 12%-23% so it was hardly being taxed. After staring at my the Resource Monitor for awhile I noticed that the Maximum Frequency of my CPU was at 60%. In a nut shell what it means is what the efficiency of your CPU is running at; so mine was running at 50-60% of it's capability.  Curious why this was I started poking around my bios and found an option for Overclocking Protection which was enabled. Decided to disable it about 10 seconds into booting my PC instantly shut off.

The Problem

My CPU was under clocking it self in order to save itself from burning out due to the additional heat. Protected by the bios setting to due this it opted to under clock itself rather than simply shutdown to keep cool. I decided open up my case and take a look at my CPU and found that there was a thick layer of caked on dust over the entire top of my heat-sink under the CPU fan. I wish there were a little more obvious hardware monitoring tools that would identify these issues so it would take some of the guess work out of identifying hardware issues.