The original idea behind Sherlock was a much longer series of one hour episodes, and to prove it could be done, Steven Moffat and Mark Gatiss created and filmed a pilot episode a few months before the three part 90-minute films came about.

Fortunately for them, the BBC wanted a reshoot and a new format, so this one hour version of A Study In Pink was surplace to requirements. It finds its way, though, onto the DVD Boxset, available from 2Entertain.
http://hotfile.com/dl/65299290/66232d0/sherlock.s01e00.unaired.pilot.dvdrip.xvid-haggis.avi.html