It used to be a pain in the ass to get a serial code at all (after Bil left), but now when you buy a Vocaloid their serial code comes right in the email with the download instructions. Idk if the V4 code would come with the V2, but if not I bet you could just email em for it. Ever since I had to email Yamaha complaining when they never sent a Ruby serial a while back, they seem willing to at least humor Vocaloid fans.