No$gmb is a emulator for gameboy, pocket gameboy, super gameboy, and color gameboy, allowing you to play any gameboy game on your PC.
The program is entirely written in assembler language, which makes it fast enough to run on older computers, for monochrome games a 386 with at least 33Mhz should be suggested, and for color games a 486 with something like 66Mhz.
The official webpage for NO$GMB is nocash.emubase.de