Hacking Windows Pinball is an excellent article about reverse engineering a Windows program; namely, the standard Pinball game that comes with most version of Windows:
It’s not really really difficult but it is really really tedious. And potentially spirit-crushing. So, it that’s your thing then read on, otherwise – get back to pinball!
He mentions cheats for the game, but how he found the cheats is the informative part, if you didn’t know how to do it.