When I bought my Acer Extensa 5420 it did not come with a back up cd of Vista. I have Windows Vista home premium. I had to reformat due to a virus being on the computer I didn't know what to put on so I put on an old version of XP. I want to reinstall Vista and I have my product key for it. Is there anywhere I can go to download Windows Vista Home premium being I already have the key? Please help!