This should work with 2 different Windows accounts (or Windows usernames or profiles or whatever you want to call them). Each has it's own library. But libraries may point to music outside the users User folder that you want to share.
I have been trying to get this figured out for several days now with no luck. We have been syncing our phones to two different computers with two different iTunes accounts in the past but we bought a new computer with Windows 7 on it and would like to be able to connect both of our iPhones to the new computer. I have read that in order to do this you need to create 2 user accounts. I have done this and the main account has access to the music library and the second account doesn't. How can I get access to the music in the other account? This shouldn't be this hard.