Hi...
I had this issue also and found this through Google.
Ok, nothing here helped my issue so I thought I would report what did resolve this for me.
I changed the default location of the stored messages.
I created a folder called Outlook Express.
C:\Douments and Settings\My Name\Local Settings\Application Data\Outlook Express (just to keep it close to default in Win XP Pro)
Click the following in Outlook Express:
Tools > Options > Maitenance
Locate this: Click here to change the location of your message store.
Click on "Store Folder..."
Click "Change"
Navigate to the folder you created and hi light it.
Click "OK"
Click "OK"
Reboot.
It will rebuild your message store to the chosen one upon restarting Outlook Express.
This worked for me and I hope it may help someone else.
Thanks...