The mailhost file is installed with your MSN software. If this file is missing or damaged, MSN shows a "Mailhost file" message. To enable MSN to find the file:
Click Start, and then click Run.
- Or -
Click Start, and then click in the Start Search box.
Type regsvr32 c:\progra~1\msn\msncorefiles\mailui.dll in the text box, and then press ENTER.