Hi, first and foremost give up tv dinners lol. they are worse for you than they are for the m/wave. Ok any residue of burnt plastic is going to stink for ever more and under the activity of microwaves will burn and cabonise and arc and destroy the glass tray. You could try warming the tray on CONVECTION to soften the plastic, If your m/w has convection good if not try the main oven, but be careful. To get rid of the worst of the smell in the m/wave bring to the boil 2 litres of water for 10 minutes to which you have added 2 large or 4 small lemons, quartered and zested and a dozen or so whole cloves. You may still smell a residue of the plastic but it should not taint your food, if that's the correct term for tv dinners. (sorry could not resist that) hope this helps
kindest regards
B.E.S. Microwaves
01424 447799
patrick
March 2009