Outlook Express error after IE6 upgrade

Client has Win98SE and IE5.0. Client contracted klez virus, which was successfully removed. Upgraded IE from 5.0 to 6.0 which went fine! Reboot and got an error:
Oemig50.exe linked to missing Advapi32.dll
RegOverridePredefKey.

Checked and restored Advapi32.dll – no diff.
Everytime Outlook express is started this error shows up! Click OK – the dialog error box closed and it all works fine!
Whats with the error and how do I stop it!