Get DJGPP (its a free compiler with a nice IDE called RHIDE). You can get it from http://www.delorie.com/djgpp/
The 320x200 256 color mode was a graphics mode used when DOS was the in thing along with other tweaked ModeX's.
Or if you want to go along the Win9x road and take advantage of the latest graphics cards and accelerators then try to learn a bit about the various API's out there. DirectX 6.1 gives you a generic framework to interface lowlevel 2D graphics, 3D, input, sound, network, etc. This means you don't have to write code for every piece of hardware under the sun. You can get the SDK from Microsoft's website at www.microsoft.com/directx under developers serction (I think they are making you pay for it now though and saying it covers the cost of a CD as an excuse).
Another good one to learn is OpenGL (an open source graphics library developed by Silicon Graphics Inc.) which is a popular, portable 3D library.
There are more specific APIs for certain graphics cards like 3dfx's Glide aswell.
Most (half decent) games nowdays use a combination of a few popular APIs.
[This message has been edited by BigBird (edited July 16, 1999).]