I'm not sure if this is the best place to ask this, but here goes:

Every single time I open Microsoft Word (Office 2003), I get the
following text box:

"Microsoft Office Word [in border of the message box]"

"This file contains macros with an expired or revoked signature.  Since
you are running under high security level, these macros will be disabled."

Is there any way I can find the source/cause of this?  This happens even
if I just start Word without opening any document files at all.  It also
happens every time I start Outlook (because that opens word as the
Outlook E-Mail editor).

I am concerned that something may have infected my system; I had some
kind of critical problem a couple weeks ago, the system would shut down
immediately after starting, and I did have to restore from an image
backup.  The restore (from a Drive Image backup) was drive C:, which
includes the program files folder, but on my system the My Documents
folder (which has all the Word files) resides on drive E:, which was not
restored.  Extensive scanning (both AV and spyware) show the system to
be clean, and it is perfectly well behaved in all regards except for this.

Thanks