If you put a shortcut to your app in the start->startup folder, it'll start after the PC is booted. If you want it to live within TouchSmart, you'll have to put TouchSmart's shortcut in there; however, you won't be able to disable a person from using the other TouchSmart apps nor going to windows.

Since you don't want the other apps and don't want the user to go to windows, I'd suggest not implementing your app as a TouchSmart tile, but as a full-screen app that disables alt+tab, etc.

--Andrew

It will depend on the language you are using, but at any rate, I'm sure there's a wealth of information out there. I'd try searching for:

make a [programminglanguage] application full screen
disabling alt tab using [programminglanguage]
creating a kiosk application

--Andrew