An unknown error has occurred. Error Number: 0x800C0133

Error Number: 0x800C0133 = a corrupt Inbox.

Move any mail you wish to save to a local folder you create. Then delete the problem Inbox as follows.

Tools | Options | Maintenance | Store Folder will reveal the location of your Outlook Express files. Write the location down and navigate to it in Windows Explorer or, copy and paste it into Start | Run.

In WinXP, Win2K & Win2K3 the OE user files (DBX and WAB) are by default marked as hidden. To view these files in Windows Explorer, you must enable Show Hidden Files and Folders under Start | Control Panel | Folder Options | View.

With OE closed, find the Inbox.dbx and delete it. A new one will be created automatically when you open OE.

General precautions for Outlook Express:

Do not archive mail in the Inbox or Sent Items. Create your own user defined folders and move the messages you wish to save to them. Empty Deleted Items folder daily. Although dbx files have a theoretical capacity of 2GB, I recommend about a 300MB max for less chance of corruption.

After you are done, follow up by compacting your folders manually while working *offline* and do it often.

Click on Outlook Express at the top of the folder tree so no folders are open. Then: File | Work Offline (or double click Working Online in the Status Bar). File | Folder | Compact all folders. Don't touch anything until the compacting is completed.

Turn off e-mail scanning in your anti-virus program. It is a redundant layer of protection that eats up CPUs and causes a multitude of problems such as time-outs and account setting changes. Your up-to-date A/V program will continue to protect you sufficiently. For more, see:
http://www.oehelp.com/OETips.aspx#3