I was trying to install the new synergy but it's not compatible with the newest version of Windows. You can also try "InputDirector" if you'd like to take the alternative.
There's also a version with a slightly different GUI that work on Win7 - Synergy+ (not developed any more).
Working version can be download here:
Synergy is a simple program allowing you to share one mouse/keyboard on many computers
(one mouse/keyboard for many computers with separate screens)
Note: there's a problem with mouse scroll (wheel) on some hardware. Nothing can be done with it - in case of InputDirector & Synergy+. Try attaching a different mouse if you experience such a bug.