Norton 2010 Antivirus Does Not Work As Well As The Old Norton Antivirus Corporate Edition

I had been using an old version of Norton Antivirus Corporate Edition along with Webroot Spy Sweeper with great success until Norton Corporate "died" in mid May, 2010.  Until that time I had few virus problems and would occasionaly run a manual Webroot scan to remove spyware when my computer speed slowed down.  I am running Windows XP Home Edition Service Pack 3.

 

I replaced Norton Corporate with Norton Antivirus 2010.  Now I have to run a Webroot scan every day or so and a Norton full system scan (at 12 - 16 hours) every week to maintain a decent level of computer speed.  The Webroot scan normally finds spyware and the Norton scan normally finds security risks.  I keep Webroot shut down because it slows my computer down if it runs in the background, so I understand how spyware can infiltrate my computer.  However, I leave Norton Antivirus running at all times so I don't understand why Norton does not intercept and quarentine the security threats before they become a problem.  Computer speed always improves a lot after a Norton full system scan followed by a Webroot scan.

 

What do I need to do differently to elevate the current performance of Norton Antivirus 2010 combined with Webroot Spy Sweeper to at least equal the performance I had with Norton Corporate combined with Webroot?  So far, I am very disappointed with Norton Antivirus 2010.

 

Thanks for the help.