NOTE: You must be logged on as Administrator or as a member of the Administrators group in order to perform this procedure.
Click Start , click Run , and then type the following command:
NOTE : There are no spaces at all in the preceding command line.
Click OK to open the INF folder.
Locate the file MSOE50.inf .
Right-click the file, and then click Install . This will reinstall the files that Outlook Express needs to proceed normally.
It will ask you to put your windows XP cd in the drive