How can I degrade internet explorer version 6.0 to version 5.0
To the best of my knowledge, you can't.
Tip #94: Bring Back Your Old IE Version
Have you experienced problems after upgrading to a new version of Internet Explorer? Sometimes, the best solution is to regroup, uninstall the upgrade, and return to your IE previous version. To go back, double-click Control Panel's Add/Remove Programs icon and choose the Internet Explorer entry from the list. Then click the Add/Remove button and choose Restore the Previous Windows Configuration. Click the Advanced button to get rid of Windows Media Player, Outlook Express, and all the Setup files.
that from here
I think you wull have to go into add/remove windows components to find Internet explorer !:)
Big B, oldversion only has IE versions 1, 2, and 3, which were the old stand-alone versions of IE. IE 4, 5, and 6 have always been integrated into Windows, making it hard to revert back - it's built into the kernel!
You can actually remove those versions from the Kernel. I've seen a program that will strip them out for you, and it's free.