I don't want to do this, my son does. He's looking at buying a new laptop, with Windows 8, but he wants to go to IE8.
What problem is he trying to achieve. Downgrading to IE8 is a means to and end, not an end in itself. Instead of trying to fix the problem of how to downgrade to IE8, what problem is he trying to solve in the first place, since downgrading IE is almost certainly the wrong solution for the problem he's facing.