Problem:
This happened to my dad's computer I figured out the solution yesterday. Apparently nothing came up when I searched for the solution. This works on Windows Xp (should work on Windows Vista/7) as well.
Basically when you try to open up an attachment (insert extension name here) it would open up another program, in this case it opened up Windows Live Mail **Add a Contact** dialog because of which It was harder to fix the issue.
No matter what you did, repair, updating etc. it wouldn't fix the problem.
Solution:
Windows Xp>
Go to Windows Explorer, Tools > Folder Option
Switch to File Type tabs and look for the file extension. In my case it was PDF.
Click on Advance and the pick your PDF reader, (Adobe Acrobat Reader).
Click Okay, restart Outlook and you're done. Repeat this step for other extensions and select the correct program.
Windows 7:
Start> (Type) File Type
It will take your the dialog called Set Associations. Highlight the file extension and click on Change program and you're done.
Hope this helps.
Comments
Glad you got it sorted bro.