Vista - Computer Freezing Stephen

Hi,

Windows XP Home

After experiencing a severe trojan issue (that was able to disable my Norton
antivirus) I found that I had no choice but to start with a clean slate so to
speak, so I made a backup of all my files and kids files onto an external
hard drive. Then I formated my hard drive and reinstalled XP.

I then reloaded all my programs and also 2009 Norton antivirus with
antispyware. It has been atleast a week since doing this and as of yesterday
I began experiencing a sudden slow down with the computer and then minutes
later everything froze up. The first time it happened my daughter was on Face
Book and then later that day I was performing a Norton scan and minutes
later noticed that the program had frozen up. I could not access anything!
About an hour ago I experienced the same situation. It has happened if I am
on line or not. I press my reset button and everything loads up but my icons
are slow to pop up on my desktop screen. Everything initially seems slower
to load up than usual.

Any suggestions or ways to determine what is messed up would be appreciated.

Stephen