There are many operating systems, most of which can be used with any simple PC,
in this list, you will only find the ones that serve very small markets or they are quite marginal at present, but this can be their strength.
Many more can be found on OS News or on freeos.com
- FreeDOS: free immplementation of the DOS, also available on cdroms. Useful for flashing BIOS, and running dos tools supplied by hardware manufacturers
- DR-DOS / OpenDOS: open-source implementation of Digital Research DOS
- Sun Solaris: if you have expensive Sun hardware, or want to use Solaris-only applications, Linux is more useful on older hardware and x86 CPUs
Marginal and Special Purpose