[erc007]

I think that if you want an analysis of your play, you have to give more info relating to your table position. I think that raising to T24K is fine with 77 from MP (especially late MP, ie: after 5-6 folds.) I would not however raise this hand from UTG or UTG+1 unless I was ready to fold to a reraise. IMO, being all-in w/77 is fine if you are sure that you are against two overcards, but even bad/reckless players can pick up TT and JJ too. You're in ok shape as far as your stack goes your "M" is 15 - (see Harrington on Hold 'em Endgame) indicating that you're going to have to get aggressive with med pairs and high-cards at this stage. It's a fact of online tourneys that you're going to have to win a race or two (or 5 if you're not getting dealt) to cash. In the late stages of any tourney, you have to be ready to play any hand that you open with to the end, once I open with 77, I have made up my mind that I'm calling a raise unless it comes from the tightest player at the table.
I think that it might help you to analyze beforehand what you are going to do if you get re-raised.