E521 desktop suspends, restarts wtih "change your battery"?

Here is the text from the event logger:

Event Type:    Information
Event Source:    Application Popup
Event Category:    None
Event ID:    26
Date:        8/2/2009
Time:        2:08:04 PM
User:        N/A
Computer:    LOUIS-461C0FECE
Description:
Application popup: Critical Battery : You should change your battery or switch to outlet power immediately to keep from losing your work.

For more information, see Help and Support Center at http://go.microsoft.com/fwlink/events.asp.

The same event is in twice.  What could be causing this since there is obviously NO battery for power in a desktop?

Thanks