After installing IE8 I broke Virtual Earth on my laptop, even after rolling back I still could not view a page with the Virtual Earth control on it – I would get a javascript error with the control. Since IE7 is built into Vista there is no way to reinstall it. Instead the solution is much easier, just reset it.
Under Tools -> Internet Options -> Advanced Tab -> Big Reset Button.
It essentially restores it back to default, keeping your favorites but not much else. Fixed my problem in seconds.