major oses other then the big 3

[Calum]

it was strictly GUI. ibm paid microsoft for DOS licences, microsoft started developing windows (a frontend GUI for DOS) after it saw Macintosh, IBM also saw macintosh and paid microsoft to develop OS/2, a totally graphical system (like macintosh) but IBM were pissed off that microsoft totally legally also continued to create and market windows, so much so that IBM got angry and stopped hiring microsoft's services to write software for them.

OS/2 is widely regarded as a bitch. if it didn't cost $300 i would have tried it myself, it has the dubious bonus of being able to run PCDOS and Windows 3 programs as well as its own.

[AdmiralAK]

Hmmmm.....
BeOS is not dead. The company is gone and the Assets were sold off to Palm however the public domain version of BeOS 5 is still that, public domain. From this public domain version (which was not that different from the Professional version), a few people have made distros of it.
BeOS MAX Edition and BeOS DevEd are two of those distros. Also a company is making the YellowTab OS (Also known as BeOS R6).
Then there is BlueEyed OS which is using the linux kernel to be a BeOS like OS with the BeOS look and feel.


OS/2 is nice. I have versions 3 and 4 (god bless ebay and the cheap prices I bought them at    ) -- The original prices are insane. There are some apps for it and I do use it occasionally.

Finally, the AtheOS/Syllable project seems to have a big following out there, although  I have never tried them.

[ChakanTGM]

ShellCity has a list of non-windows/linux operating systems. Check it out.