KDE as X Term on XP controlling Linux box

This week I have built my fileserver, setup SimplyMepis (KDE/Debian  
based distro), and I can access files from both XP and OSX accross my  
LAN.

I have also installed KDE on Cygwin on my XP box, and that is  
working... I can browse the web with Konquerer and edit files with  
Kate.  Not a bad start.

The next step is to be able to have my XP box run as an X Terminal,  
so I can continue to work on the linux fileserver.  I want to shove  
the box up in a cupboard somewhere asap, but I can't do that untill I  
can get remote access to it.

All I really want is to be pointed in the right direction.  I'm  
amazed I got this far and have no clue how to proceed.  Any websites  
would be helpful.  I've done google searches, but havn't actually  
found anything that tells you how to do it.  (plenty that say it can  
be done though).

Thanks for putting up with the newbie :D