This problem is driving me nuts.

Ideally, I'd like to be able to open each Excel file in a separate process,
separate window, giving my users the ability to work with the Windows side by
side. Knowing this isn't possible or easy, my users have become accustomed
to opening two instances of Excel.

The problem I have occurs when people are opening Excel files attached to
email messages in outlook or when double-clicking a file from Explorer.
Before our upgrade to new PCs and Windows Vista, if the user wanted to have
two files open side by side, they would open two Excel instances. To target
a particular window, they would simply give focus to the Excel instance in
which they wanted the document to open. Double-clicking the attachment in
Excel or Explorer would open the document in the window which last had focus.
This worked beautifully.

Now that we have upgraded to Windows Vista, this method no longer works.
Launching a file by double-clicking the file always opens in the file in the
first instance of Excel without regard for which Excel instance last had
focus. For opening files from Explorer, we have a workaround; we can simply
drag and drop the file to the desired instance. The problem occurs in
Outlook; there is no way to open an attachment except in the default instance
of Excel.

Can anyone tell me how have these files open in a new window? I'm trying to
find a well supported method thatr doesn't involve breaking DDE applications
and hacking the registry.

Thanks.