IA-32 PC emulator

 Bochs is a highly portable free IA-32 (x86) PC emulator written in C++, that
 runs on most popular platforms. It includes emulation of the Intel x86 CPU,
 common I/O devices, and a custom BIOS.
 .
 Bochs is capable of running most operating systems inside the emulation
 including GNU, GNU/Linux, *BSD, FreeDOS, MSDOS and Windows 95/NT.