Do you get the same problem if you open excel in Safe mode:
Close excel
windows start button|Run
excel /safe
file|open your book.xls
File|close (no changes)
If you get prompted, I don't have a guess. If no, then maybe you have a macro
that's helping out.
Chip Pearson has a page that can help you find that helpful macro:
http://www.cpearson.com/excel/StartupErrors.htm
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There have been a few problems associated with Google's Desktop Search. Do you
have that installed on your pc?
If yes, maybe disabling that COM Add-In will help.
One way to turn it off:
In excel,
Tools|customize|Commands tab|Tools Category
Scroll down the commands listbox and
Drag "COM Add-ins..." to under Tools|Addins
(It seems to make sense there.)
Then close up that dialog.
Back to Tools|COM Add-ins...
Turn off the google desktop search addin.
(You could use a registry tweak, too. But I think that this is safer/easier.)
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This google addin shows up in other Office applications, too. You may want to
look at disabling it in those other office programs, too (well, if you
experience problems).