Slow performance or stopped full system scanning

My Norton Internet Security 2011 has greatly slowed to a
stop in the past few days. I also noticed that my CPU meter has been stuck
between 99% and 100% while full system
scan
is running. In my last attempt, I left full system scan running for
ten hours, and I have yet to complete scanning. And I have to log-off to cancel
the scan.

 

I tried uninstalling and reinstalling Norton 2011, using the
Norton removal tool and down loading NIS-ESD-18-6-0-29-EN.exe. But there was no
appreciable difference in performance.

 

Norton Technical Support recommended the following procedures,
which I also tried. I uninstalled non-Symantec security programs (I found
something called “Malware”). I deleted temporary files and the contents of the
Prefetch folder. I ran LiveUpdates. And I ran Check Disk to fix file system
errors.

 

I tried to alter the Hard Acceleration as recommended, but
my display driver did not allow changes to be made to the current settings.

 

My operating system is 32-bit Windows Vista Home Premium; my
machine is a Dell Inspiron 530, and up to now, I’ve never had a prior problem
with Norton Internet Security.

 

What has gone wrong?