Wow. Loaded question. Need a lot more details I think.
1) what version of MSIE5 did you install? Go to your HELP - ABOUT box in MSIE 5 and read the number out of there.
2) did the "update" you put in contain Outlook Express?
3) Click on my name and see if Outlook Express pops up (same as clicking on any link that is a MAILTO tag.)
4) right click on your Outlook Express icon you use and select properties. Does the path the program look like where it is installed on your hard disk? (It may have updated Outlook Express and moved it to another located leaving your older version inoperative.)
5) re-install Outlook Express from your original disk if you still have it. This would be a last resort as it may well blow away your updates.
6) check micorsoft's knowledge base (just search the microsoft site) to see if they have a fix or patch for Outlook Express. Sometimes applying updates to Outlook Express by itself will correct your problem.