This music is the Prelude in C minor (BWV999) by Johann Sebastian Bach, originally a keyboard work for Lute-Harpsichord. It is often called the Little Prelude in C minor to distinguish it from the keyboard preludes in his Well-Tempered Clavier. This Guitar version is transposed to D minor to better suit the instrument's tuning although you will notice that it actually ends in the key of A minor. On mfiles we also have the original keyboard/piano version of this prelude.
The video below illustrates the guitar arrangement using a "piano roll" style animation. Below the video you can play the mp3 file and see the sheet music below that. Downloads of the PDF sheet music, mp3 file and midi file are available via the links in the left-hand menu.