Is one of my upgrades to NIS 17.5.0.127 corrupted?

I have two Windows XP Home SP2 pc's using NIS 2010.  Each was updated from version 17.1.0.19 to 17.5.0.127, as confirmed in Help/About.  And each seems to be operating mormally.

 

However, on one pc I see that in C:\Program Files\Norton Internet Security\Engine there is only one top-level subfolder, called 17.5.0.127, and its size is about 57mb.  But on the other pc, there are two top-level subfolders of C:\Program Files\Norton Internet Security\Engine:  It likewise has one named 17.5.0.127, but it is only about 2mb, while there is a second folder named 17.1.0.19 that is about 55mb.

 

I don't understand why there is a difference, and more importantly whether there is any reason to be concerned, and if so what I should do.  As you might expect, I am more concerned about the pc that still has the large folder named 17.1.0.19.  FWIW, I had to reinstall NIS 2010 on that one about a week before the upgrade occurred. 

 

Any advice would be appreciated.