Symptoms:

When you click a mailto: URL in IE or outlook many IE windows pop up with an error action cancelled. The following error also pops up

"Could not peform this operation bebacuse the default mail client is not properly installed"

Cause:

1. the Mailto handler is not setup correctly
2. Missing URL protocol registry value
3. incorrect registry permission for the mailto handler

Reset the default E-mail client

Windows XP:

1. Goto Start -> Run, then type control inetcpl.cpl
2. Select the programs tab and from the email dropdown select a different mail client and click apply
3. Redo the previous steps and set your preferred email client again

Vista:

1. Goto Star ->default programs
2. click set program access and computer defaults
3. click custom and select your amil cient the click ok
4. Click set your default programs and select yourmail cient from the list
5. click set this prgoram as default and select ok

If those setup do not solve the problem please proceed

Create the missing string value

1. goto start->run and type regedit.exe
2. goto HKEY_LOCAL_MACHINES/Software/Classics/mailto
3. select new from the edit menu and then click string value
4. type URL protocol as the name of the enw string value
5. exit register editor

Set correct permission for the mailto key

1. goto start-> type regedit.exe
2. browse to HKEY_LOCAL_MACHINE\Software\Classes\mailto
3. goto edit menu and select permissions
4. Make sure users have read access to the mailto key. Administrator and system group should have full control over the key
5. If any object is missing click add and add the user or group
6. click advanced and select replace permissions entries on all child objects with entries shown here that apply to child objects check box
   
7. Deselect the inherrit from parent the permissions entries that apply to child objects.
8. click apply then yes then OK