You could set up passwordless SSH for putty.
I was able to set it up in a few minutes using this tutorial (you can skip the pageant step).http://www.dailyiteration.com/howto-pas ... ith-putty/
To the saved session you create in the above tutorial, also, turn on x11 forwarding, and set the "remote command" field in putty to be the command to start your x11 app. Your app can now be accessed from a Windows shortcut to "putty -load <session name>". No typing required, at all. I tested this a minute ago using "xcalc" as my remote x11 app. Double click a windows shortcut and I've got a x11 app running off a remote client.
Downside to this is that you'll have to do a one time setup of putty and the public key stuff on each machine. Depending on how secure things need to be, you may also need to set up an account for each user on your Linux box.
Sorry if the above is a bit incoherent and rambly... Not usually awake at this time.