The below answer is what TomWij was trying to say. I have just put it in a step-wise manner.
To configure Outlook as your default email program in Windows Vista and Windows 7:
- Click Start.
- Type "default
programs" in the Start Search box.
- Click Default Programs under Programs in the search results.
- Now click Set your default programs.
- Highlight Microsoft Office Outlook or Microsoft Outlook on the
- Click Set this program as default.
- Click OK.
Make Outlook Your Default Email Program in Windows 98, 2000, and XP
- Start Internet Explorer.
- Select Tools | Internet Options from the menu.
- Go to the Programs tab.
- Make sure Microsoft Office Outlook or Microsoft Outlook is
selected under E-mail.
- Click OK.
If you are bothered about ""no default mail client" error in Office 2010"
To resolve this issue, you must first
remove the corrupted Outlook registry
key, and then perform a Detect and
Repair operation to have Outlook
rebuild the key. To do this, follow
these steps.Important This section,
method, or task contains steps that
tell you how to modify the registry.
However, serious problems might occur
if you modify the registry
incorrectly. Therefore, make sure that
you follow these steps carefully. For
added protection, back up the registry
before you modify it. Then, you can
restore the registry if a problem
occurs. For more information about how
to back up and restore the registry,
click the following article number to
view the article in the Microsoft
Knowledge Base: 322756
) How to back up and restore the
registry in Windows
1. Click Start, and then click Run.
2. In the Open box, type regedit, and then press ENTER.
3. In Registry Editor, locate the following subkey in the registry:
4. Select the subkey, and then press DELETE.
5. Click Yes.
6. Quit Registry Editor.
7. Start Outlook.
8. On the Help menu, click Detect and Repair.
9. Follow the instructions on the screen to complete the repair.