Excel 2013 sometimes opening new tab

[pmonett]

I have this weird case at one of my client's sites. All users have been migrated to Office 2013 from the previous 2010 version. For some users, and not all the time, when they open an exiting workbook, it opens in a new tab instead of a new window. They would like to always have a new window.

I'm at a bit of a loss, because I had been brought to think that 2013 didn't really allow a choice. I can't find any Options or Registry entry that would control that behavior either.

Any ideas ?

Thanks in advance,

Pascal.

I've got nothing to hide, and I demand that you justify what right you have to ask.