Once upon a time, I find out by accident that I can use the run dialog box (Win+R or Start -> Run) to open folders in outlook directly, folders such as the inbox for a particular mailbox or the calendar. Outlook allows the user to set the default folder on start, so this would not be much of an issue if you only use one outlook window However, I often have both the inbox and calendar window open, and it is a hassle to open the second window by finding the mail folder and right clicking it to select the "Open in new window" option.
But over time, the shortcut stopped working and I could not figure out why. Revisiting the issue on a recent googling finally yields an answer. Here are the two relevant article that solved my problem:
http://www.slipstick.com/problems/outlook-missing-outlook-protocol/
http://www.slipstick.com/outlook/using-outlook-links/
Basically, for me, the newer version of windows (since XP) no longer register the "outlook protocol" on install. According to the articles linked above, there seems to be other situation where this no longer works as well.
To fix the issue, you would need to edit the register to manually register the outlook protocol. The articles tells you how to do this. Alternatively, you can save the following into a ".reg" file, such as "outlook.reg", and then double click it to enter the information. This works for me for Windows 8.1 running outlook 2007. You will have to change the path of the OUTLOOK.EXE file.
Windows Registry Editor Version 5.00
[HKEY_CLASSES_ROOT\outlook]
@="URL:Outlook Folders"
"URL Protocol"=""
[HKEY_CLASSES_ROOT\outlook\DefaultIcon]
@="C:\\Programs\\Microsoft Office\\Office12\\OUTLOOK.EXE"
[HKEY_CLASSES_ROOT\outlook\shell]
[HKEY_CLASSES_ROOT\outlook\shell\open]
[HKEY_CLASSES_ROOT\outlook\shell\open\command]
@="\"C:\\Programs\\Microsoft Office\\Office12\\OUTLOOK.EXE\" /select \"%1\""
To use this, I usually open the Run dialog box via Win+R, and then enter outlook:inbox or outlook:calendar. If you have inbox or calendar under different pst files, you will need to do something like outlook://myPSTFileName/Inbox.