set up ScreenRecycler to use a PC as a second monitor

Ive downloaded ScreenRecyler because I want to use my old PC as a second monitor. However there is not much support on the ScreenRycler webpage and I cant get my PC VPN guest to detect the ScreenRecycle.
If any one knows how to configure s you can use a PC as a second monitor using ScreenRecycler please tell.
Also if ypu know about alternative solutions to SR post them.