Cannot start Microsoft Outlook. Unable to open the Outlook window.

Let's just say it, I'm not the biggest fan of the Microsoft Outlook/Exchange world out there: frankly speaking, I'm far more inclined to use - and suggest the usage of - open and freeware e-mail client software suites such as Mozilla Thunderbird. Despite all this, I'm often struggling with Exchange and Outlook issues because there are a lot of private and public companies that seem to be absolutely unable to avoid using it, even if they could save a fair amount of money migrating to cheaper (and more robust) cloud-based or linux-based collaboration suites such as Google Apps, Zimbra, Zentyal and the likes.

Given the above, let's talk about one of the most annoying problems you can encounter when working with the most dreadful e-mail client you can think about.

The issue

The problem I'm talking about often occurs when the PC crashes with Outlook being open, but it can also occur if the software is unable to properly shutdown itself, which is something the user might not always be aware of. Anyway, the next time he tries to open it, an error popup is raised containing the following obscure message:

Cannot start Microsoft Outlook. Unable to open the Outlook window.

Not bad, huh? That's one of the main reasons why I don't like Outlook: the useless error messages, never really connected to the problem source.

The fix

The above issue is most likely related to the Outlook navigation pane being broken. In case you don't know, it's the tree navigation bar to the left containing all the account, e-mail and folder nodes: in short words, the Outlook's most important element. To fix that, you need do the following:

• Close Outlook.
• Open the Windows Task Manager and be sure to terminate any (still) running   OUTLOOK.EXE  instances using the Terminate button.
• Open a Command Pompt with administrative priviledges.
• Navigate to the Outlook installation folder: C:\Program Files\Microsoft Office\Office15\ for Office 2013, \Office14\ for Office 2010, \Office12\  for Office 2007 and so on. For further info regarding the Microsoft Office default installation folders, read here.
• Input the following command:

By doing that you will fire a new Outlook instance and reset the navigation pane to its initial (default) state. Needless to say, all modifications made to the navigation pane layout will be lost: for example, if you're using Exchange public folders, you will need to manually go to the View menu panel and make them appear again, since they're not shown by default.

That's it for now: happy Outlook (so to speak)!