Windows 7: HP Pavilion dv7 Using 100% CPU idling at desktop

I've had my dv7 for nearly two years, and it has worked well the entire time. Recently within the last month, when preforming normal tasks like browsing the web or watching videos, the CPU usage would spike to 100% and stay there, rendering the computer useless. Every time this happens I would shut it down and wait a full day. This allowed for about 15 minutes of smooth running time before another spike.

I have run CCleaner, two full system scans using Norton 360 to no avail, updated all BIOS, cleaned out the fan and heatsink, and checked the power settings to see if the processor had been changed to use a minimum 100%.

Computer specs:
Processor: Intel i5 M 460 @ 2.53 GHz
RAM: 4GB
OS: Windows 7 64Bit
Gfx: HD Radeon 5650 (integrated)

Any ideas or help would be greatly appriciated.
Thanks.

What applications and services are running in the background?

Fairly basic things:
Rainmeter, Skype, BitTorrent, Norton Security.
Things of that nature.