Uninstall Internet Explorer 8 and install Internet Explorer 6

"Uninstalling IE8 on Windows XP

Click the ‘Start’ Button –> ‘Control Panel’ –> ‘Add or Remove Programs’.
Find and select Windows Internet Explorer 8 from the list of software, click on the ‘remove’ button.
Restart Windows.

Removing IE8 on Windows Vista

Click the ‘Start’ Button –> ‘Control Panel’ –> ‘Programs’ (Programs and Features)
Select View installed updates
Find and select Windows Internet Explorer 8 from the list of available updates, click uninstall.
Restart Windows.

How to Reinstall Internet Explorer 6 or 7?

After you restart your computer, open Internet Explorer. The icon is still on your desktop.
In Internet Explorer, go to ‘Help’ –> ‘About Internet Explorer’
If Internet Explorer 6 or 7 appears in the About Internet Explorer dialog box, then you’ve successfully uninstalled IE8.

Source:

http://www.geckoandfly.com/2009/06/30/uninstall-windows-ie8-and-reinstall-internet-explorer-6-or-7/"

"IETester will do what you want ...

However I would have a talk with your lecturer.

I would have serious concerns with any course syllabus that requires downgrading back to a browser that was released in 2002, because what they are teaching would no longer be relevant.

The syllabus should be updated to use a current version that confirms with ECMA standards."

"You can get all versions of Internet Explorer at Final Builds Site - IE Collection
and have them installed at the same time, then choose your default
or try Browser Compatibility Check for Internet Explorer Versions from 5.5 to 10."

If you're on XP, you can install Multiple IE

"You should be able to go to the control panel - > Add Remove Programs

Find IE8 in the list and uninstall. This should roll you back to version 7. Go back to add/remove programs and uninstall IE one more time. This will roll you back to version 6.0
That is all there is to it!

Happy Hunting"