Yep might as well stop there, even NullDC or Demu won't be of any use to you.
First of all your CPU is an ancient piece of crap, won't run Dreamcast games anywhere near playable speeds.
The only emulators you would be able to run is PS1, SNES, Nes, Genesis, Atari emulators and even PS1 emulators might have some minor slowdowns, considering your graphics hardware is integrated Intel crap PS1 emulation might not run well either.
You can give up any hope of Dreamcast, PS2, or Gamecube emulation with decent performance. Your computer just isn't up to the task of emulating these systems nor does it have the raw power needed to emulate these systems at acceptable speeds.
Secondly and lastly as suspected, you have Intel integrated graphics which is only good for rendering the desktop, and even then it sometimes fails. It fails at rendering in both PC games made in the last eight years and emulators. Not only does it render in PC games and emulators with such poor performance, it also fails to render graphics properly in Gamecube and Dreamcast emulators as well as some PC games.
I'm also going to guess your graphics hardware doesn't have adequate Pixel/Vertex Shader support or doesn't support any Pixel/Vertex shading, this is a hardware feature that is required by most if not all new PC games and applications.
You need a whole new system, best to avoid any pre-built systems as they are ususally crap and build your own with more recent hardware. Instead of spending $600 - $1200 on a new system that can play Dreamcast games with decent performance and some compatiblity issues, you could opt to save money by going with the cheaper solution by purchasing a used Dreamcast and games if you don't have one already.