Windows shares are by user, not by machine, so you can't restrict it to just the Windows 10 machine.
The easiest way would be to connect to the administrative share on the Windows XP machine. You will need the user name and password for an account with Administrative rights on the Windows XP machine. Then on the Windows 10 machine run the following command:
NET USE T: \\XPCOMPUTER\C$ /user:USER PASSword
Where XPCOMPUTER is replaced with either the name, or IP address of the XP computer and USER is the user with Administrative rights on the XP machine and PASSword is the password for that account.
The result will be that the Windows 10 machine will now have a T: drive that is the C: drive of the Windows XP machine.
This is just what I need. But when I run it, I get:
System error 5 has occurred.
Access is denied.
Here's the command as I entered it:
net use T: \\Joe-WinXP\C$ /user:Joe 8a6c9e
I was careful to use the correct case for all letters: "Joe-WinXP", "Joe", and "8a6c9e". I also tried:
net use T: \\Joe-WinXP\C$ /user:Joe PASS8a6c9e
net use T: \\Joe-WinXP\C$ /user:Joe PASS 8a6c9e
Because I wasn't sure why PASS was in all caps and "word" was not. The first got the same Access denied. The second got a syntax error.
As far as I know, user "joe" has Admin privileges. I am able to install software using that login. If I open up the User Accounts applet in Control Panel, it shows user account "Joe" as "Computer administrator".