Granting X-Window acces to your PC using Cygwin or ReflectionX or HummingBird Exceed:

1. Edit file: /etc/X11/xdm/Xaccess

Change from:
# * #any host can get a login window

To:
* #any host can get a login window

2. Edit file: /etc/X11/xdm/xdm-config

Change last line from:
DisplayManager.requestPort: 0

To:
!DisplayManager.requestPort: 0

3. Edit file: /etc/X11/gdm/gdm.conf

Change last line from:
[xdmcp]
Enable=false

To:
[xdmcp]
Enable=true

4. Restart X-Windows

[root]# init 3
[root]# init 5

For RHEL 5

Remote Graphical Desktops and XDMCP

If you have installed the X Window System and would like to log in to your Red Hat Enterprise Linux system using a graphical login manager, enable the X Display Manager Control Protocol (XDMCP). This protocol allows users to remotely log in to a desktop environment from any X Window System compatible client (such as a network-connected workstation or X terminal). To enable remote login using XDMCP, edit the following line in the /etc/gdm/custom.conf file on the Red Hat Enterprise Linux system with a text editor such as vi or nano:

Add the line Enable=true , save the file, and exit the text editor. Switch to runlevel 5 to start the X server:

/sbin/init 5