Using Cinema Display with a desktop PC
I actually do this at work with an HP Z620 Workstation running Ubuntu Linux at 2560x1440 resolution. It works like an absolute charm. I used this adapter from Startech:
You plug it in the back of your PC and the other end connects to the mini display port connector. Keep in mind that the cable is short (6") so you have to make sure that the cable coming out of the Cinema Display will be long enough to reach your PC.