I'll have to play with jum52 as I think that might be a better solution for me. Doesn't play all the ROMs that Atari800Win can, but it also doesn't ask me what type of cart it is...big plus.
As for loading ROMs...first, you need to download all the Atari ROMs, for the 5200, XL, Basic, etc. There's four of them you need total. Then, if you are going to use the UI, it's File-Attach Cart. Otherwise, I've been using the commandline... "atari800win 5200 -cart whatever.bin"
I'm going to see if I can use Howard's wrapper to get jum52 to quit with one keystroke. Then I'll be okay I think...