I use a software emulator to play ToD on my Windows. There are quite a few emulators out there, and most of them are listed at http://www.99er.net/emul.shtml. I've had the best luck with MAME.
Here are some tips for running ToD under MAME.
If you want to start MAME from the prompt, the command line that works for me is:
mame64 ti99_4a -cart tundoomg.bin -r 800x600 -nohws -gamma 0.85 -sr 22050 -ioport peb -ioport:peb:slot2 32kmem -ioport:peb:slot8 tifdc -flop1 tunnels.dsk
When you get the
LOAD DATA FROM menu, choose
DISK1 and type in
QUEST or the name of your saved game.