What you need to do is change these registry keys either using Registry Editor (regedit.exe) or using Windows Scripting Host or other program that allows editing of the Windows Registry.

[HKEY_LOCAL_MACHINE\SYSTEM\ControlSet001\Control\Terminal Server]
"fDenyTSConnections"=dword:00000000
"TSEnabled"=dword:00000001

As with all Windows Registry Editing - take care as you may end up breaking your computer.

Now you will need to add users the to local Remote Support User group. This can be done by using the Computer Management Console, Batch scripting, or if you really like, Windows Scripting host.

This command will add a Domain user to the local security group.  Remember that you will need to be a local administrator of the machine so that you can add users to local groups.

net localgroup "Remote Desktop Users" %USERDOMAIN%\administrator /add

It is easy to adapt this command so that local users can be used instead.  Just remove the %userdomain%\ bit from the command.

If you want to use Windows Scripting, then you can use the following file, just save the file with a .VBS or .WSH extention.  VBS can be ran as a computer startup script in Active Directory Group policy.

' This script adds users to the local Remote Desktop Users security group.
' Script is free for anyone to use.

' Create a Network Object so that we can access local and network security info.
Set oWshNet = CreateObject("WScript.Network")

' Get the current Domain and Computer name that is calling the script.
sNetBIOSDomain = oWshNet.UserDomain
sComputer = oWshNet.ComputerName

' Create an Object that will link to the Remote Desktop Users group
Set oGroup = GetObject("WinNT://" & sComputer & "/Remote Desktop Users,group")

' suppress errors in case the user is already a member
On Error Resume Next

' Create a Network User object for the Administrator.
' Note: replace Administrator with a username of your choice
Set oUser = GetObject("WinNT://" & sNetBIOSDomain & "/" & "Administrator" & ",user")

' Call the Group Object Add command to add our user to the group.
oGroup.Add(oUser.ADsPath)

' Create a Local User object for the Administrator.
' Note: replace Administrator with a username of your choice
Set oUser = GetObject("WinNT://" & sComputer & "/" & "Administrator" & ",user")

' Call the Group Object Add command to add our user to the group.
oGroup.Add(oUser.ADsPath)

' Error catchall
On Error Goto 0

Use this information at your own risk.  For full details about using Scripting, visit http://www.microsoft.com/scripting