telnet 192.168.0.51 5900 from 192.168.0.52 does not work (time out). The same command on localhost DOES work.
This look like a firewall issue to me.
To test winvnc you can just copy winvnc.exe to the server pc and vncviewer.exe to the viewer pc. All other files are not required to make
a connection. No registry changes are needed.
schooks makes it faster, cad.exe allow to ctr-alt-del when running as service..... but first you need to be able to connect.
Try to execute
netsh firewall add portopening TCP 5900 blah enable
on server AND viewer