If the key path does not exist, create the key path. To create the key path, locate and then select the following registry key:
HKEY_CURRENT_USER\Software\Microsoft

Click the Edit menu, click New, and then click Key.
Type Office, and then press the ENTER key.
Click the Edit menu, click New, and then click Key.
Type 9.0, and then press the ENTER key.
Click the Edit menu, click New, and then click Key.
Type Outlook, and then press the ENTER key.
Click the Edit menu, click New, and then click Key.
Type Security, and then press the ENTER key.
Click the Edit menu, click New, and then click String Value.
Type the following name for the new value:Level1Remove

Press the ENTER key.
Right-click the new string value name, and then click Modify.
Type the extension of the file type that you want to allow access to from Outlook 2000 as follows:.exe

To specify multiple file types, use the following format:

.exe; .com
When you are finished, click OK.
Exit Registry Editor.
Restart your computer.