We are not aware of any virus that would play the song "Fur Elise". However, some PC motherboards play this tune when there is a hardware problem. Check your motherboard manual.
For more info, see the homepage of Diamond Flower Instrument: http://www.dfiusa.com/music.asp :
Musical Warning Damage Free Intelligence (D.F.I.) is a feature we have added to our newer motherboards to warn users of some classes of hardware related problems. It is a warning system on the motherboard that plays a warning tune if certain hardware problems are detected. Some users hear strange music coming out of the PC speaker and think they have been hit by a virus - they scan the hard drive multiple times and reformat it, but it just will not go away. The user now thinks that they have been infected by a virus that no virus scanning software can detect today. This is not the case at all. The standard alarm/tune/music that they may hear is a variation on "Fur Elise." Our production motherboards use this tune whereas pre-production/prototype boards may use other sound chips. There are three main sets of reasons that the alarm/tune is playing - Processor, Heatsink/Fan and Power Supply related.
Disinfection & Removal
Technical Details: Mikko Hypponen