This applies only to Windows95 and Windows NT. The difficult part is restoring the previous value for this setting in the registry. You can do this by:
1. Re-installing your mail client. or 2. In your NOTES.INI there should be a setting OldRegKey_MAILTO this should contain the previous setting for the registry key HKEY_CLASSES_ROOT\mailto\shell\open\command.
Using regedit, you ca restore the previous value. ONLY USE THIS METHOD IF YOU ARE FAMILIAR WITH USING.