No, don't buy a copy of Home Premium... do you have an Anytime Upgrade Disc? That will work to do a straight install with the product key on the machine. You can also get the DVD from Microsoft for 9 bucks!
https://na.windowsanytimeupgradestore.com/W...IRECT/Home.aspxJust select "Windows Vista Home Basic" from pull down, then "Choose Windows Vista Home Premium", then "Do you have a Windows® Anytime Upgrade disc?*" (select NO), then click the red X by "Windows Vista Home Basic to Windows Vista Home Premium" then you are left with the disc alone. Fill out the info, they will ship the disc. It contains all versions of Vista 32bit and 64bit. I have mine, works like a charm!
-Scott