Your question was not easy to understand (but it was much better than what I could do if I was trying to describe a problem in Spanish).
If I understood you correctly, you are using XDMCP to make remote connections from one Unix workstation to another. This is working successfully.
I then understood that you were trying to use this method to connect to a Windows 2000 box, and you failed. This would be expected, since Windows 2000 PCs do not typically support XDMCP.
A good tool for connecting remotely between Unix and Windows boxes is VNC.
Here is a link with further information: