Go for it ....... I'm sure you can .... following a trining programme gets you there slowly but surely ....
Although I am one myself who thinks it may be on the too hard basket just yet ..... I've got a plan to run one before I'm 40 which gives me until the end of 2012.....
I never thought I could do it a half myself but a friend talked me into it and I did it and she didn't!!! .... I would recommend John Bingham's book Marathons for Mortals .... if you haven't read it already .... I found it very entertaining and inspirational

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Perhaps you can inspire me .... when I get a little more in shape to start really thinking about this goal too ....