Sudden increase of 150MB in XP's commit charge

Xp Pro Sp3 w/ all updates -- NAV 2011 w/ all updates

 

Normally, after boot and a few moments of 'settle down' time, the commit charge on my desktop is about 285-295mb.  This is typical and has been that way for the past year or so.  If, then, the commit charge suddenly goes up with 140-150mb and stays that way .. what's the 1st thing to suspect?  A virus, malware or similar?  Or, that a process of NAV 2011 kicks in, like the Idle Time Optimizer?  After using NAV Classic for a year, I installed NAV 2011 Standard mid-May.  Only thereafter did I experience these problems .. once after the large XP hotfix early June and one after a rather minor program install last week.

 

As the high comit charge didn't go away after cold/warm reboot, after some days I restored the boot drive with an image done just before the problem(s) started .. and in both instances the commit charge returned to normal.  Then, I noticed that I hadn't turned off the IdleTime Optimizer (since done).  Could ITO really be the culprit?  If so, how much memory is used when it runs?  And, how come ITO runs immediately on boot .. and before the Automatic Task Delay period?  Or, is ITO not coverred by ATD?

 

Best, CBA