Windows 7: CPU rising to 100% and PC eventually slowing down

After working on my PC for 10 to 15 minutes the CPU shoots up to 100% and it becomes very slow. It even takes minutes to open a folder. Even if i close all applications, still it does not come down. It remains stand still at 100%. I am using Windows 7 ultimate 32 Bit. My desktop configuration is Intel core 2 duo 2.8 GHz, 2 GB DDR2 ram, 250 GB h/d, Asus P5kpl-am/ps motherboard and a Nvidia Geforce 8400 GS graphic card[512 MB] ..
I am using Windows 7 ultimate [x64 version] , on my laptop. Its a Dell Inspiron 15R, the configuration is Intel Core i3 M380 2.53 GHz, 4 GB DDR3 Ram, 500 GB H/D...But here its working just fine... I just can't figure out the problem... And yes, I am using Kaspersky Internet Security 2011 [Licensed Version] in both of them... Please help me...

Did you look in the "Windows Task Manager", you may need to show processes from all users, to identify the process that pegging the CPU?

Before the CPU creeps up, right click your Taskbar and select Open Task Manager. In Task Manager, set it to "Always on top" from the Menu bar. Then Select the Processes tab and set the CPU column with the high users to the top. When things start to go pear shaped you should be able to see if you can spot what it is.

Snap! Cr00zng

Usually when I see issues like this it's the Antivirus, anti-malware, or a combination of the 2 "fighting" each other. One thing you can try is running msconfig, click teh "Startup" tab, and uncheck everyting there. Reboot and see if its better. If it is, re-enable one at a time. If not, click the "Services" tab, check the "Hide all Microsoft Services" box, tehn uncheck all the remaining services, and reboot. Then you can one by one add back until the problem re-occurs.