Can install iTunes 4 without changing iTunes 3?

[Henri]

I'd like to install iTunes 4 and start experimenting with the new 
format to find my preferences. I have about 15 gigs of MP3s recorded 
at 192 in my current iTunes 3 and synch it often to my wife's iPod ( 
5 gig) and my own 10 gig, to change music collections. (I am saving 
the 20gig for AAC's, wife gets the 10 gig and the 5 becomes an 
emergency disk once the whole plan works out). I am short on time 
these days so I want minimum complications and confusion, since I 
anticipate mutiple copies of same songs recorded at various bitrates 
as I experiment with 4.

When I go to install iTunes 4, the only option I see is to upgrade. 
So I quit and query the list. Do I need to "hide" the iTunes 3 
somewhere? Do I need an external disk? (No room for another 
partition).

This query may sound familiar. I posted it once and repsonse was I 
didn't need to do it. Well, I've thought it over and I do want to do 
it this way. Can you advise?