you can download x-win32 from http://www.starnet.com/products/
the Xaccess file is usually here if you use xdm: /etc/X11/xdm/Xaccess I do believe you can use the hostname or IP (just one line per host or IP) just don't put a star * (all hosts) on a line by itself or you are inviting anyone to your X server. If the file is not there you can do this from the command line: locate Xaccess and it should give you the full path of the Xaccess file you are looking for.
Then just start the X-Win32 X server and configure it (the options are pretty straight forward and simple) just play around with it and find out what works best for you.
when using the query you would NOT be in xterm you would be logged out of gnome or KDE (on machine A) and be just at the command line maybe in a virtual terminal could work I cant remember right off hand. once you run the command it will show you a login screen and you will be using machine B as you would if you were in front of it with a keyboard and monitor and just booted up to that machine. you wont have to SSH to it or anything.
One more thing to add is if you are doing this over a private network thats cool. over the Internet I like to tunnel X over SSH. there are a few pretty good tutorials on the Internet that give you step by step on how that works. here is a pretty good one here: http://www.cag.lcs.mit.edu/~wentzlaf/faq/ssh_X.html
once you have configured this successfully you can use secureCRT to ssh from a windows box to a linux box and make sure the box is checked to forward X11 packets and from SecureCRT you can run a command like evolution& , kmail& or any X program and the program will open up on your machine like you were running it from your machine. in a nice separate window.
One thing to remember- http://www.google.com
is your Friend! I use Google for everything. thats how I found that tutorial
Hope this helps.