I'd go with Mike-Bracknell
Wouldn't even bother trying to fix it - You have no idea what system files are there and whats been blown away during the update.
Best bet is to install Vista from scratch. Take the hard drive out, put it in another machine as a secondary disk. Youl then be able to grab all of your documents off.
I work for HP (all be it for their unix server support area) - I think we had some issues with a few laptop models regarding the batteries, there was a recall programme a little while ago. You might want to see if your laptop is one of the affected models. See -
HP Notebook PC Battery Pack Replacement Program - Click the May 14 link.
Hope thats of some use.