That's generally true for all apps and computers. PCs have have different BIOS, different hardware, different drivers, etc. Some apps may not work on all PCs.
The Mac is just another PC as far as Windows is concerned. Boot Camp supplies the drivers for Windows to operate with the Mac hardware.
The fact that plenty of pirated copies of Mac OS X are running on Dells, HPs, etc., is further evidence of Mac's capability as a PC.
Are there special versions of OSX that run on PC’s? I’d like to try it before buying a while apple system only to find out I don’t care for the OS.