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: %systemroot%\inf
NOTE : There are no spaces at all in the preceding command line.
Click OK to open the INF folder. Locate the file MSMsgs.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