I didn't answer the poll because it allowed me only one choice.
On my #1 hardware station (19 inch tall tower) I have a mutliboot system where I select which OS to boot using OpenSUSE's boot-choosing program (i forgot the name of the pgm already), and I usually boot to Windows XP Pro (Microsoft), but I can also boot to OpenSUSE (Linux), Open Solaris (Unix), or Windows Server 2003. I also have VMware Server (is that the correct version name?; the free version, that runs under Linux or Windows) running under Windows XP, and under that I have Windows Server 2003 and Open Solaris. It has 2 hard drives, a 750 gig for all the OS's and data, and a 500 gig where I put compressed backups. I am planning to upgrade the Windows XP Pro OS on this device, to Windows 7.
On station #2 (15 inch tower) I can boot to Win Server 2003 or Win XP Pro, using Acronis' boot program (I forgot the name of the pgm again). I use this unit for printing, to a laser page printer, via a a parallel port (LPT1). I also have a color inkjet hooked up via usb port.
On station #3 (14 x 13 x 4 inch compact desktop case) I have XP Pro only. I have a POTS modem in this unit and use it as a fax machine.
I also have an obsolete laptop which has little or no practical usefulness, on which I have Win XP Home. It came with Win XP home, but even with a brand new deployment of the OS, and very few programs installed, it takes too long to boot and does everything too slowly. Odd.
My dedicated gps device (TomTom) has a Unix or Linux operating system. I forget which
My wireless router (Buffalo) has a unix or Linux op sys.
I've used a Mac system at work.