CPU Usage frequently 100% even though it seems not even close tototal memory

I have an Acer Aspire 5315 laptop on Windows Vista. I installed a 3G
RAM. It has a 1.73 GHz Intel CPU.

Often the computer gets very slow and windows task manager will show
CPU usage 100%. I counted the Memory (Private Working Set), the total
of these running is never more than 0.5 G RAM.

I did virus scan by avast! and do not have any virus.

Please help and suggest.

 

Which Image Name does Task Manager show to be using the CPU.

Steve

 

Try booting into safe mode and see if you still get the same slowdowns.
You can get safe mode by hitting the F8 key on a reboot. If it does, then
the logical conclusion would be programs running in startup. You can
disable all of these without affecting windows itself by running
"msconfig" and disabling the startup there.

 

Click on the "CPU" tab in "Processes" to sort by which one is using the most.

Write back with your findings.