This isn’t going to be detailed…
Get PsExec from SysInternals (http://live.sysinternals.com/psexec.exe)
psexec remoteComputerName cmd /c netsh firewall set service RemoteAdmin
This runs the “netsh” command on the remote system to enable RemoteAdmin through firewall. I ran into this problem when I couldn’t run the netsh from a 2003 box to control the XP remote system. Strange. No time to research it any further right now.