We have a few Windows(XP & 7) and Ubuntu machines in the house sharing a wireless connection, and want to share music between them. If possible, I would like to be able to serve music from both Windows and Ubuntu (but it doesn't have to be the same time).

I don't know much about sharing folders or streaming, but I'm guessing both would be options (that is, using a local client to access a shared song or a local client to access a shared stream). I want to be able to share the music between the systems as simply as possible.

Bonus points (but not requirements) for

• cross-platform -- same application on both Windows and Ubuntu?
• available on startup (via daemon or autostart or whatnot)
• open source

More info:

• All systems have dynamic addresses (DHCP) supplied from the ISP-supplied wireless router.
• There are several Gigabytes of music on one Windows XP box and one Ubuntu 10.10
• The music is not well-sorted (I'm thinking this might have an impact on UI usability).
• Only has to be available internally (private address space behind the wireless router)
• bandwidth is not a problem
• We don't have (legitimate) admin access to the wireless router