debugging directx apps

I thought about putting this over in game programming, but that forum doesn't get read as much, and this isn't really specific to programming games. If someone thinks it should be over there anyway, feel free to move it :rolleyes:

How do you go about debugging a fullscreen DirectX app? Stepping through is obviously not an option. I saw an article on Flipcode or Gamedev or something suggesting using two monitors for debugging DirectX apps - that's not an option because I have neither the space nor the money for a second monitor. I have error messages being written to a file in my program, but that only catches the errors that I program in - it doesn't really tell me exactly where the problem starts like stepping through could. Basically what I've been doing when something is wrong is staring at the code for a long time, tweaking things, and running again, to see if it behaved differently. It's quickly becoming a horrible way to debug. Does anyone have experience/suggestions for debugging fullscreen DirectX apps? There has to be a good way to do this that won't cost me a ton of money... right?

Yeah, I'm usually trying to debug something I did with the API, or debug something which interacts closely with it :-/ I have other PCs around, but not really any that I can use. I don't see how it would help anyway.