Lars Ulrich of Metallica could be a very happy man today -- the fate of Napster, the widely-popular online song-swapping service which he and other musicians have been protesting, could be decided sooner rather than later. A federal appeals court is expected to rule today on whether or not to slap an injunction on Napster that could effectively shut it down, according to Reuters. The decision comes more than four months after an Oct. 2 hearing on the landmark copyright infringement case in which recording industry giants (including BMG, Warner, Universal, EMI and Sony), asked that Napster, which was created in 1999 by former Northeastern University student Shawn Fanning, now 20, be ordered to stop enabling users to swap songs for free. At the hearing, Napster squared off against the Recording Industry Association of America (RIAA), which requested the court lift a stay on an injunction ordered last July against the service, which has attracted over 50 million users. Since the lawsuit was first filed in December 1999, Napster's service has continued to gain popularity. To date, it has amassed nearly 60 million users who use it to swap songs for free by trading MP3 files, a compression format that turns music on compact discs into small computer files.