If you are looking to just take over a session and control what is going on, Remote Desktop will work in this situation. You would just need to enable remote desktop on both ends.
However, if you have someone sitting in front of the PC and you are remote, wanting to show them something, you will need an alternative solution. Logmein will allow for that kind of situation. This, or some other third party solution, may be the only way to do what you are doing if you cannot upgrade the machine from XP Home to anything Professional.
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