IE 5 is the first Microsoft app that can fix itself without a complete reinstallation when things go wrong.
If the browser is acting strangely, head for the Control Panel (Start-Settings-Control Panel) and open Add/Remove Programs.
Select Microsoft Internet Explorer 5 and Internet Tools and click Add/Remove (don't worry, you won't uninstall anything).
In the next dialogue box, click Repair Internet Explorer, then click OK. Follow the prompts to let IE figure out what's gone wrong.