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When you try to run Outlook then you may get the following error message:

Unable to open your default e-mail folders. An unexpected error has occured. MAPI was unable to load the information service CSTMSG.DLL. Be sure the service is correctly installed and configured.

If you get these errors then Outlook will be unable to start at all. To fix this problem then please follow these steps:

- Restart your PC, and log back into Windows
- Open Windows Explorer and goto the following directory C:\WINNT\patches
- In here there should be a file called con_outlook_904210.dat.
- Delete this file Rerun the Outlook installation, and once completed then Outlook should work