You don't have Mcafee email scanning on?

that

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

Make sure Show All Messages is the only item checked in View | Current View.

Some general OE advice:

Do not archive mail in default OE folders. They will eventually become
corrupt. Create your own user defined folders for storing mail and move your
mail to them. Empty Deleted Items folder regularly. Keep user created
folders under 100MB, and Default folders as empty as is feasible.

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.

In Tools | Options | Maintenance: Uncheck Compact messages in background and
leave it unchecked. {N/A if running XP/SP2}.

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.

Clear the Temporary Internet Files often. In IE | Tools | Internet Options |
Delete Files button. And check the box to Delete Offline content.

And backup often.

Backup and Restore:

http://www.insideoutlookexpress.com/backup/

http://www.oehelp.com/backup.aspx

http://www.oehelp.com/OEBackup/Default.aspx