Sharing screens/monitor between Asus Laptop and iMac I have the following equipment:


An iMac 27" (mid-2011 windows 8 BOOTCAMP with 2 thunderbolt port and 1 miniDisplayPort)
An ASUS ROG laptop (with 1x VGA port/Mini D-sub 15-pin for external monitor / Mini display-port / 1 x HDMI)
An External monitor with HDMI, VGA and DVI input.


I want to use the display on my iMac as a 2nd screen from my asus laptop, leaving the iMac to use the external Monitor instead of it's own screen.  Essentially, I would like to use the iMac screen as an external monitor while still having the iMac running a full OS, not just being used an a monitor.  Is it possible for this iMac to either a) receive input to be used as an external monitor, and b) if so, can it still be used as a computer at this point?
I'm afraid that's not possible...

The closest you can get to that is by using Target Display Mode as described here. The problem, though, is that TDM is only available when running OS X on the iMac. Furthermore, you won't be able to use the iMac even though it's technically running. 

Judging from this question here at Ask Different, TDM doesn't seem to support multiple displays while running anyway.

I've looked at this before and did some research for this question, and I was unable to find anything beyond streaming the contents in an AirPlay-like fashion, which I doubt is usable in your case.