High cpu usage when converting and burning

Okay i got a new computer. Its specs are AMD athlon 64 X2 dual core processor 4400+, 2 gig of ram and a standard edition NVIDIA Geforce graphics card 6150. My problem is this. When i first got the computer i could use convertxtodvd winavi cucusoft avi to dvd converter or any one for that matter. Never had a problem would convert and burn fine at like 30% Cpu usage. Now a couple months later it runs at 100% cpu usage and will shut down after 5 minutes. Doesn't matter what program i used. Trust me I've tried em all and it does the same thing so I'm guessing its not the software its the hardware.I'm running windows vista.The computer stays running all the time.Do you think that is the problem....that maybe the parts are being burnt out sooner because its left on all day and night? I heard it was good to leave it on to not burn out the parts but maybe i heard wrong.What programs do you recoomend to monitor such things or is there any way to run a hardware diagnostics check on all that stuff to narrow it down with whats causing the problem? Ok for spyware i use lavasoft and i have norton internet security and antivrus. I use ccleaner to clean up the computer and fix registry problems. I run the spyware and anti virus check probably 2 or 3 times a week along with all the computer clean up and i also go through internet options and clean it that way.I have the fully installed working version of everest. I ran a couple of the programs like i would normally and had everest running in the background. Without the converting software CPU #1/Core #1 85 degrees celsius and CPU 2/ COre 2 103 degrees celsisus before i turned off the program... when nothings running they both sit at 30 degrees celsius and a little under. As soon as it hit 65 degrees the fans kicked on.