Many VirusDef subfolders hogging drive space

I’m trying to free up some space on a hard drive on a desktop PC running XP and NIS 2009.  This folder contains almost 4 gig of files:

C:\Documents and Settings\All Users\Application Data\Norton{0C55C096-0F1D-4F28-AAA2-85EF591126E7}\Norton\Definitions\VirusDefs

There are 52 sub-folders, each containing over 70 MB, named by date (e.g. 20090601.003), going back to early May.

For comparison, I checked another PC also running XP and NIS 2009.  It only has 74 MB in the VirusDefs folder and only one subfolder named by date 20090601.003.

I’m thinking that the desktop PC with many dated subfolders has a problem - it should be clearing those subfolders.  

How can this problem be resolved, is there a setting to change, does NIS need to be uninstalled/reinstalled?  Can I eliminate all the subfolders except for the current date 20090601.003 ?

Thanks in advance,
Scott