Now this is ust my opinion based on what I have done in the past....If I were you I would wait for next year ammend your 07 return at that time, it will help you out then on your 08 return....Ammending your 07 return will not really do much for you you may get another small return check, but use it for a deduction for 08...
Since you haven't yet written it off yet it still an unrealized loss so it would be for the 2008 tax year if you will write it off this year. It's not like an IRA where you have until April. Anything over $3,000.00 you can carry over as a capital loss in 2009. That's if you live in the US of course.