Does this happen when you're starting excel or does it happen when you do
File|Open from within xl?
Does it happen when you double click on a file (in windows explorer) with xl
open or when excel is closed?
I'm gonna guess that it happens when you start excel (maybe by double clicking
on a file in explorer).
Excel loads files in your XLStart folder and addins that are checked under
Tools|Addins.
It kind of sounds like there's a workbook that's trying to open and that
workbook wants to run a macro in book1 (book1.xls???) named Test5.
If my guess is ok, then I'd move all the files out of the XLStart folder and
uncheck the all the addins under Tools|Addins. (Keep track of what you did so
that move the good ones back.)
Then one-by-one, move things back and restart excel to test. If/when you find
the culprit workbook/addin, you can decide what to do later.
Chip Pearson has more notes at:
http://www.cpearson.com/excel/StartupErrors.htm