For a while now, I’ve been running two versions of Office on my corporate laptop with no problems – Office 2007 from our corporate “gold brick” image and Office 2010 (mostly for functionality I’ve got very used to in Outlook).  After a recent “Patch Tuesday” I started to see some strange behaviour whereby, depending on the method of invocation used, sometimes a 2007 version of an Office application would open, and sometimes a 2010 version.

I’ve had the media and keys for Office 2013 for a while (a properly licensed copy but not supported by our IT department) so I decided to remove 2007 and install 2013.  Because I figured the new UI would take a while to get used to (actually, it hasn’t) and because I wasn’t sure if any macros, etc. would run in the latest versions of Word and Excel (still a possibility), I elected to install 2013 alongside the existing 2010 installation.

It all went swimmingly, until I was having issues with Outlook, which is quite happily connected to our Exchange servers but telling me it isn’t when I want to update my out of office settings or view a colleague’s calendar.  I started to look for Outlook 2010, and found it wasn’t there any more…

Of course, being me, the first thing I did was tweet my bemusement and, being Twitter (and despite being 9pm on a Friday night) I quickly got some responses which told me why (thanks Aaron and Garry).

For those who can be bothered to RTFM, check out Microsoft knowledge base article 2784668 (“Information about how to use Office 2013 suites and programs (MSI deployment) on a computer that is running another version of Office”) or, for a workaround, there’s a TechNet forum post called Outlook 2010 gone in side-by-side installation with 2013″.

<tl;dr>

Outlook 2013 cannot coexist with any earlier version of Outlook. Unless you want to try a complex click-to-run setup…