Your post appears to have an error in the name of the DLL. But no, Microsoft didn't do as you wrote but they don't backup your files either.
We only lose what we don't backup.
If you run the Control Panel, Add/Remove programs and select IE/OE then take its REPAIR option.
-> http://support.microsoft.com/default.aspx?scid=q270670 tells how to backup and restore. If you don't, that's your choice.
I have Windows 98 at home, I'm not there at this time, because Outlook Express won't open due to the above problem. HELP!!!!!!!! Is there any way to recover this lost file? Does Microsoft, whom I have already emailed and received not one word, put expiration viruses into their programs so they don't work after a set number of years? I am frustrated to have to wipe my hard drive clean or reformat as I will then lose all my email files and the addresses in my address book. Thank you anyone who has an answer!