Summary: I bought one of these a couple of years ago and used it to attach a second monitor to my desktop PC. I used it for Windows 7, Windows 8, and then Windows 8.1, and it worked well for all operating systems. It attaches to a USB port of the PC and creates a VGA port for the second monitor.
Summary: I have this running my 2nd, 24" monitor on a Dell Optiplex 3020 i3. It works perfectly, with one little caveat: the computer won't start with it plugged in. If I unplug it, start the computer, I can plug it in immediately and (when Windows comes up) it works fine.
Does not support OS 10.9 or later, customer service is not helpful.
Devin Halleran, Amazon
4 December 2014
Summary: I use a MBP. The product worked adequately for a while, although there was quite a bit of lag time to my second monitor. However, the product stopped working after the upgrade to Mavericks. I called customer service back in October 2013 and they said they were "working on it.