I see that Gary Weber has created a program called nomenu.nec that will keep your NEC from returning to the Menu when you power on the computer. Well, here's a simple and easy method that I have verified to work on both the M100 and T200. It takes up at the most 4 bytes.

Put your left hand above the ASDF keys and get your right hand poised at the power switch. Roll your fingers on the keys and at the same moment turn your Model T off. If you time it right, (and it's hard not to) then the act of typing the characters in will prohibit your Model T from returning to the Menu. The secret is that you have to turn it off after you hit the A key and before you hit the F key. It's not as hard as it sounds. Try it. I don't have a NEC, but I imagine it would work for the NEC as well.