I am running Excel2003 routinely; I am set up with 'Windows in
Taskbar' unchecked so that as I click on multiple *.xls files (say in
Windows Explorer) only one instance of the application is open and all
spreadsheets are visible in the Window pull down menu. I recently
installed Excel2007 and only want to run this on specific files, so I
changed the file associations so that 2003 opens xls files....
My problem is that now whenever I click on an xls file, a new instance
of Excel is launched; what I want is for a single instance to list all
open spreadsheets. The puzzling part is that the 'Windows in taskbar
box is still unchecked! I also opened my Personal xls and made sure
the box was unchecked there as well. It's almost as if there is a
default set by 2007 somewhere and is not controlled by the Tools/
Options/View dialog. I'm not real comfortable in the Registry,
although I did find a post by Gord Dibben (I think, apologies if I
misquoted) detailing Registering and deregistering versions that I
might try if all else fails.

Thanks much for any insight. John