I did that to my microwave. It turned the whole inside yellow. I think I put baking soda inside to try to absorb the smell, and I wiped it out really well. The color never changed, but the smell eventually did go away. Micro still works fine.

Stick a bowl of vinegar and water in there and let it boil for about 3-5 minutes, just to loosen up as much as possible. Then give it a good scrub with a paste of vinegar and salt. Rinse.

Wet down some paper towels with bleach and stick them to the scorch marks. They'll stay put. Leave them for several hours. Rinse thoroughly.

Stick some lemon slices in a bowl of water and let it boil for 3-5 minutes. Don't open the door, just let them sit for a few hours to really freshen things up.

I've read (but not personally tried) that acetone-free nail polish remover will remove it faster than the bleach.

Thanks, I'll try your advice. I'm so mad at this woman, as this was a brand new microwave. :(

Knew I could count on the GWers! Came home late this afternoon to discover that the DH had come home for lunch and burned (not just scorched) something in the microwave. He had cleaned up what he could before he had to go back to work, but the top and sides of teh mwave and the center of the glass turntable were black and the burned smell was awful. (He told me later that one of our salad plates was destroyed, too.) I made a bee-line for the computer and did a GW search which turned up this and other threads on the subject. Zapping a cup of vinegar then wiping out the mwave has removed most of the smell. I spread some soda on the turntable and have closed it up for the night hoping that it will absorb more. Tomorrow I'll get some acetone free nail polish remover recommended on the other threads. I'll test it on a small spot to see if it will clean the scorching without disolving the lining. ;-(