This can be the result of many hard-to-troubleshoot things. Start with these:
1. Check your hard drive for errors. This is done with Scandisk utility in Windows versions prior to Windows 2000. In Windows 2000 and later, right click C: drive in My Computer, choose Properties, select Tools tab, and click Check Now button, and select all options, choose Yes when prompted and reboot computer. To see results of scan, you'll need to look for scan event in event viewer in Control Panel>Administrative Tools. If errors are found, visit hard drive vendor and download and create their diagnostic disk and run that.
2. If you have webmail access, login to your mail account and delete all SPAM and any funny looking messages. Corrupt or ill formatted messages can cause problems.
3. Verify firewall software is not blocking OE traffic.
4. Visit
Microsoft Help and Support, search for "outlook express crashes" and review articles to see if any apply to your circumstances.
5. If you're running Windows 95, 98, or especially ME, it may be time for a complete computer rebuild.