I've been studying the Caterbury Tales lately and was just wondering why so many words we use now like run, fallen, drawn etc. have a 'y' in front of them in Middle English; is it to do with tense? How would it have been pronounced?

Examples:
carried = ybore
drawn = ydrawe
fallen = yfalle
led = ylad
run = yronne

P.S: Ooh, it's nice to be back - thanks, Jackie, for reminding me that AWAD still exists as I was wondering who to ask.
(oh yeah, and my website's finally up - okay, not the originally intended topic, but. See my profile)