I have vista final retail too and i tried to dual boot it with xp.But after the setup completed copying and extracting the files it showed a message that said "The setup could not update the computer's boot configuration setup cannot continue".So i had to completely get rid of xp by booting through the DVD.I liked vista so much that by now i have completely forgotten about xp.Insert the dvd into the drive after booting into xp the run the setup.exe from the dvd drive say d:\setup.exe where d:\ is your dvd drive.The select install now.Then select "Do not update setup files".Then enter Key u might skip this step but i recommend u enter a cd key as failing to do so might result in data loss.Then accept the license agreement and then finally select custom install.U will then be prompted to select the drive in which u want to install vista.And don't worry it won't delete xp but instead dual boot with it.