You can shutdown a XP Home machine remotely. The solution lies in granting the Guest account the privilege to access the shutdown. Here are the details:
To do this you need to use the NtRights.exe file found in the XP Resource Kit, here http://www.microsoft.com/downloads/details.aspx?FamilyID=9D467A69-57FF-4AE7-96EE-B18C4790CFFD&displaylang=en
Download the kit from Microsoft.
Copy the NtRights.exe program to %windir%\system32.
Next log-in as an administrator on the box to be shutdown remotely
Perform the following commands from a command window:
NtRights –u Guest +r SeRemoteShutdownPrivilege
NtRights –u Guest +r SeShutdownPrivilege
Be careful about the spelling – note there is no ‘t’ in the priv name where you would expect it to read SetRemoteShutdownPrivilege
See here for a full description of the NtRights.exe program http://support.microsoft.com/kb/279664
Now you should be able to use the shutdown.exe programs from a remote computer. When you do the shutdown message on your XP Home machine will read ‘Shutdown initiated by \\\Guest’