CharlesGrey: Off topic, why do you always say OS when you're talking about your PC? Isn't the term OS normally only used for the software side of the system, such as Windows, Linux etc. ? Perhaps it works for the hardware or entire system as well, I just don't normally see people use it that way.
tinyE: Honestly, I picked that up here. XD My hand to god people kept stopping me when I said "system" or "puter" and said "Oh you mean your OS." So I started using it. :P I had no idea there were other people who thought it sounded as stupid as I do.
If you were saying something like 'this game is not compatible with my computer', I can see people saying 'You mean the OS, right?' especially if they were trying to troubleshoot. Modern computing has got to the point that most software is compatible with most hardware with the right OS, and they might have been interpreting your use of 'computer' as the hardware.
Technical pedantry incoming!
OS = Operating System, the software that makes your computer work and provides a standard way for programs to interact with the computer hardware. Games are typically compatible with an OS, not specific hardware.
System or Computer = often used to refer to the hardware side. It can refer to the entire OS/hardware system, but some technical people may cringe or misunderstand when you do that. 'Box' is a more specific way to refer to hardware only.
/terminology nazi