From: http://www.realvnc.com/pipermail/vnc-list/2002-March/029502.html
once you have ran vncserver once (to setup your user account)
Modify the xstartup file in your .vnc directory (under your user account)
To have KDE come up in the VNC session:
change the last line from
tvm&
to be
startkde &