I started running around two years ago or thereabouts - at least that's when I discovered the C25k. Prior to that, I was chugging around my local block and arriving back home needing to crash out on the sofa! Needless to say, I made zero progress that way.
Then I found the C25k in 'Mens Health' magazine and decided to give it a go. After a couple of 'false starts', I pushed myself to commit to it. I had to repeat a week from time to time, but considering where I started, finding myself able to run non stop for 30 minutes was a massive boost to confidence!
I gradually increased my distance, until one day I found that I'd clocked around 15km/9 miles in a single run! During one or two of those long runs, my knee was trying to tell me something. I ignored it: BIG MISTAKE! I went out again one night and after 30 minutes or so, my knee gave a fairly sharp tweak, so I decided to cut it short and go home - limping a bit, so I was fairly sure something was wrong. To cut a long story short, that resulted in quite a few months enforced break from running, combined with some physiotherapy.
So, I ended up having to start almost from scratch - running five minutes and then going home. While my conditioning wasn't too bad, my knee gave me trouble if I went past that. So, I gradually built up the time and distance again and now I'm running 5k plus again. My conditioning is returning as well - but it's not quite where it was before the knee niggle - the last five minutes of today's 5.69k were quite a push! I'm now doing a 5k to 10k plan and I'm going down the track once a month to see what damage I can do to my times. When I've got them to an acceptable level, a parkrun or two await! Long term, I want to do the London Marathon one day. 
Sorry for the life history essay! 
Edited: 06/09/2012 at 16:44