To enable the RDP service on Port 3389 in Windows xp, just run these commands in an script:
netsh firewall add portopening TCP 3389 RDP enable all
reg add "hklm\system\currentcontrolset\control\terminal server" /f /v fDenyTSConnections /t REG_DWORD /d 0
reg add "hklm\system\currentcontrolset\control\terminal server" /f /v fAllowToGetHelp /t REG_DWORD /d 0
NET STOP TermService
NET START TermService