You have a whole WORLD of material to work through here so you can come to your own conclusions about what's likely to work for you.

For a start, look at Keyclone (dead easy to setup, cheap but not free, but some of us have ongoing problems with it) and Multibox, which is free but less intuitive to set up.

However, if you had problems getting Synergy going, there's a fair chance that whatever stopped you doing that will also stop you getting other software working - firewall / network configuration issues for example.