I hope this might be of some use.
BOAC, Have you have tried a restore from a bit further back in time. (I''m not certain that restore overwrites everything. Have you got a recent image backup ? It might be the best option.)
(I'm on Acronis 8 for backup - But if your'e using another package say Norton Ghost, the same applies.)
I'm using the new version of Virtual box under linux (Ubuntu 9.04) on two PC's without any probs at all. But my use has been really experimental. ( Ubuntu 10.05 LTE - I do not like the new interface !)
I am about to install it on my XP SP3 box and I will let you know how I get on.
As an alternative, there's a utility called WUBI. It's an installer that claims to install/uninstall Ubuntu without the hassle of GRUB.
As yet I have not tried the utility.
CAT III