Unable to connect to WinXP c$ share

I have two WinXP Pro laptops. I have installed monitoring
software on one of the laptops and am trying to install it
on the second laptop. The monitoring software works
similar to Symantec Antivirus Corporate edition--one
computer is the server, and it does push installs to the
client workstations.

To do the push install, the server needs access to the c$
administrative share on the client computer. Problem is,
I absolutely positively have not been able to the
computers to access the c$ share.

This is what I've been trying:
c:net use x: \\computername\c$
The password is invalid for \\computername\c$

Enter the user name for 'computername': Administrator
Enter the password for computername: hit Enter
System error 5 has occurred.

Access is denied.

c:

I have tried to get multiple WinXP systems to connect to
the c$ share on other XP systems, and NONE of them have
allowed me to do so. Conversely, however, those XP
systems CAN connect to the c$ share on Win2k systems.

So how do I get these XP systems to be able to access each
others' c$ shares?