Shoutbox

Assuming you are on the school's network running windows, why not use the windows shared folder?
run the windows network setup wizard and turn on file and print sharing. The computer name will become the server name. After that, go to the properites dialog of the root folder that contains your music (i.e. 'My Music'?)
On the Sharing tab, check 'Share this folder on the network', put in a share name, and you're done.

To access the folder, in explorer type in

code:

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\\ComputerName\ShareName\

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oops, you want people to play music on your laptop...

I dunno if it can work across another computer, but party mode for WMP (comes with Microsoft Plus) sorta does what you want