Background NIS2011 Scans Out of Control

I am running NIS 2011 (v 18.5.0.125) on a Dell 4300 laptop with WinXP SP3.  I  did a trial install last year and a paid-up install in December.  A major concern with Norton products in the past has been their tendency to take over your system during "background" scans.  I ran into this problem with a circa 2005 Norton product (on an IBM T40 laptop) and a circa 2008 Norton product (on a Dell desktop).  Each time I eventually gave up and used another AV application.

 

I did a fair amount of testing during the trial period and things seemed OK.  They no longer are.  Scans that I schedule run at high priority even though I have told NIS to run at the lowest priority possible.  I have found no explict priority setting but the first time a scan runs, there appears to be a method to run at lower priority.  Now these scans take 100% of available resources.  I can pause them but can not get them to leave the system alone while I am doing something.  I completely shut off the idle time scan as once it started it took over the system.  I have run several other AV packages for a year or more and never had this problem.

 

Anyone know how to get background scans to actually run at low priority?

 

 

[edit: Fixed posting error.]