MSDN vista

okay, so my friend gave me his work email and pass to the MSDN site so i can download vista for free. I dont want to re-do everything on my computer, but i wanted the option to use vista. so i was going to put it on a new partition. But i tried this with ubuntu and had terrible experiences. if i do this with vista, will i be able to keep XP as the default OS, or even better, have it only ask if i want to use vista after XP has already loaded, rather than asking me during startup?

also, i can choose Vista, Vista Business, or Vista Enterprise. which should i go with?

keep in mind, ive already heard all the reasons why Vista=AIDS, so thats unnecessary.