"Class not registered" startup error

[GeorgeB]

Beginning a week or so ago, when I start Excel 2000, I get

Class not registered.
Looking for object with CLSID:{AC9F2F90-E877-11CE-9F68-00AA00574A4F}

This occurs whether opening an existing file, a template, or
"nothing".

Two questions; what did I do to cause it, and how do I fix it. Aside,
I got a significant spyware infection in the same timeframe, and
killing it messed up lots of things ... this problem may have occurred
along with that.

TIA, George