Open any song with WMP. If there isn't a list of tracks on the right-hand side of the window, then right-click anywhere above the play buttons and click "Show List". Then, simply drag any songs you want into the list and click "Save List" at the top. If you have the latest version that came with Windows 7, there'll be a button on the top-right of the list that looks kind of like a calendar with a check mark on it that says "Select list pane options". Click the drop-down arrow next to it and then click "Save list as...". You get the option of a couple different file-types, but I would suggest saving as .m3u, as that seems to be the most cross-compatible.