Vinagre on Desktop to WinXP. How setup?

You can enable remote controlling in XP and us tsclient. This will give 128bit security. It will lock the local screen but will give you a quick, secure connection.

http://www.microsoft.com/windowsXp/using/mobility/getstarted/Remoteintro.mspx

This will get the remote connectivity enabled. The account you connect with MUST have a password.

The link to the doc at MicroSoft was the key. Thank you so much. Problem solved. Now all I need to do is learn how to use the command line switch for geometry on rdesktop. The -f switch gives full screen, but cannot iconify it. Without the -f switch, the window is way too small. Maybe the geometry switch will give me the compomise I seek.

Thank you actionparsnip for your guidance toward my solution.
For others who may be interested in my complete solution, following are the steps I took.
My final result, using Ubuntu Desktop, was to have an Icon on the desktop. I can now double-click that Icon, just like running any other application via an Icon on the desktop, and wind up at the logon screen to my WinXP machine. And again, I am running WinXP Pro, not WinXP Home. I cannot say whether WinXP Home would work as well, but I suspect so. So, here are the steps.
First off actionparsnip did a typo which temporarily confused this neophite:
       ...... remote controlling in XP and us tsclient......
Should have read: ..... remote controlling in XP and use tsclient.......
Secondly, I did not know what "tsclient" was (being a neophite), since I was asking about the "Vinagre" remote desktop client. A Google search turned up the answer pretty quickly. Apparently this is another name for the "client" of the command line command of: rdesktop
And rdesktop is another, separate, different remote desktop client solution in Ubuntu Linux. Different from Vinagre, that is.
Using rdesktop, the resulting window was way too small for my needs. I wanted a full, or nearly full, screen to display the desktop of the remote WinXP machine. Using the -f switch for the rdesktop command took over my full screen on the Ubuntu Desktop, which was also not acceptable. So, I discovered the -g switch, played with it for while, and finally came up with this command string, which accomplished my goal:
       rdesktop -g91% 192.168.1.101
                Note: rdesktop does not allow dynamic window sizing (grabbing the lower right corner).

Now the WinXP machine had to first be set up according to the link which actionparsnip gave in his answer. Otherwise rdesktop cannot connect over to the WinXP machine.
No changes or configurations were needed on my Linksys router.
Ok, so that's all well and good, but I did not want to have to enter this command string every time I wanted to do a remote desktop over to my WinXP machine. So, that sent me off on another quest to learn how to create an Icon on my Ubuntu Desktop which would run this command string for me when I double-click on that Icon. So, here's that solution:

1) Create a script file using your preferred method to do so. I used gedit.
    The text in that script file is as follows:

#!/bin/bash
rdesktop -g91% 192.168.1.101

2) Pick a name for your script file, giving it a suffix of .sh
        So, for me it was: WinXP.sh

3) Bring up a terminal window and make the script executable. I used this command:
        chmod 744 WinXP.sh

So, now with a script created, I needed an Icon to launch that script. Again, a Google search produced the answer in pretty short order. Here's what I did:

1) Right-click out in the open desktop area of Ubuntu Desktop.
2) Choose "Create Launcher..."
3) In the "Name:" field, give the Icon a name that will appear on your desktop with your Icon.
4) I left the "Description:" field blank.
5) In the "Command:" field type in your executable script name, including the explicit path.
        For me, that was: /home/stan/WinXP.sh

6) I left the "Comment:" field blank.
7) Click the "Close" button, and look for your new Icon on the desktop.

If it doesn't work, check to be sure your executable script will launch the remote desktop. For me to have done that, I would do this in a terminal window:
        cd /home/stan
        ./WinXP.sh

If your script doesn't work, be sure that the command line command string works directly in a terminal window.
And if that doesn't work, you're probably dealing with a config issue of some sort at the WinXP machine, so revisit the link supplied by actionparsnip in his response to me.

Again, my starting setup is as follows:
    Cable Modem connected to a 4-Port, Hard-wire, Linksys router.
    My WinXP Pro machine is connected to one of the 4 ports.
    My Ubuntu Desktop machine is connected to another of the 4 ports.
    Both machines successfully get out on the internet.

Hope this saves somebody else some time.

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