Source : http://support.microsoft.com/kb/312346To resolve this issue, follow these steps:
1. On the Start menu, point to All Programs or Programs, point to Accessories, and then click Windows Explorer.
2. In Windows Explorer, edit the file type. To do this, follow these steps, as appropriate for the version of Windows that you are running:
• For Microsoft Windows XP or Microsoft Windows Millennium Edition, follow these steps:
a. On the Tools menu, click Folder Options.
b. On the File Types tab, click URL:MailTo Protocol under the (NONE) section, and then click Advanced.
c. Under Actions, click Open, and then click Edit.
d. If you are running Microsoft Outlook 2002, type the following text under Application used to perform action:
"C:\Program Files\Microsoft Office\Office10\OUTLOOK.EXE" -c IPM.Note /m "%1"
If you are running Microsoft Office Outlook 2003, type the following text under Application used to perform action:
"C:\Program Files\Microsoft Office\Office11\OUTLOOK.EXE" -c IPM.Note /m "%1"
If you are running Microsoft Office Outlook 2007, type the following text under Application used to perform action:
"C:\Program Files\Microsoft Office\Office12\OUTLOOK.EXE" -c IPM.Note /m "%1"
e. Click OK two times.
• For Microsoft Windows 98, follow these steps:
a. On the View menu, click Folder Options.
b. On the File Types tab, click URL:MailTo Protocol, and then click Edit.
c. Under Actions, click Open, and then click Edit.
d. If you are running Microsoft Outlook 2002, type the following text under Application used to perform action:
"C:\Program Files\Microsoft Office\Office10\OUTLOOK.EXE" -c IPM.Note /m "%1"
If you are running Microsoft Office Outlook 2003, type the following text under Application used to perform action:
"C:\Program Files\Microsoft Office\Office11\OUTLOOK.EXE" -c IPM.Note /m "%1"
e. Click OK two times.
3. In Internet Explorer, verify the e-mail program. To do this, follow these steps:
a. On the Tools menu, click Internet Options.
b. On the tab, change the default mail program to Outlook Express in the E-mail box, and then click Apply.
c. In the E-mail box, change the default mail program back to Outlook, and then click Apply.
d. Close the Internet Options dialog box.
e. Click Start, click Run, type mailto:, and then click OK.
DO REPLY IF IT WORKS OR DOES NOT WORK