Aitch, when I first took the plunge and joined a Rosemary Conley exercise class, some of the other members were planning to WALK Race for Life - I was too scared to join them but vowed that the following year I'd run it.
I went from not being able to run to the next lamp post, seriously that's how unfit I was, to completing 5k in July 2002. By September I was up to 10k, a half marathon followed in Feb 2003 and then I got very silly and started triathlon. Since then I've done stacks of races, from 5k to marathons, on road, trail & in kneedeep mud and can honestly say it's transformed my life - not to mention my shape, I've gone from squeezing into a size 18 on a good day to being comfortable in a size 10. It's a great way of meeting people, and no-one cares what you 'do' in 'real life', when you're out, you're a runner, plain & simple.
I also think I'm a good role model to my pre-pubescent daughter as she can see that it's ok for girls to do and enjoy sport.
So stay with us, we've all started from scratch at some stage and keep us informed of your progress!