Hi folks, I'm trying to do the same thing as the OP of this thread. Basically I'm running the game on an ancient Pentium 1 machine from like 1996, on Windows 98, and at 320x240 res the game runs perfectly, but at 640x480, its too slow on this machine and not fun...
I'm not able to set my Win 98 desktop resolution to 320x240 by itself, its just not something available in the display options, lowest I can do is 640x480, so the window takes up 1/4 of the screen... Just checking if in the 14 years since this thread was originally posted, if there might have been any enhancements to the Cave Story options/configuration, or other ideas/software that have come out that might help me run in fullscreen with the lower resolution... There are several other Win9x platformer games that allow for 320x240 at full screen with my video card, so there shouldn't be a technical incompatibility.