Does it have a recovery partition?
the best thing to do is to ring the Acer and ask them for a recovery CD. it will cost you a price but this is the way you're going to have to go. Atleast this way you'll install Vista along with all the drivers you're going to need.
other option would be to take it to a local computer shop and ask if they can reinstall it for you.
additional option: get a vista DVD and install it yourself.
note: you will need the product key (normally on the bottom of the laptop)