Remote Desktop (RDP) service in Windows XP can be used to access your remote computer from your home computer.
i-e RDP can be used for doing Support over Internet.
You can read below articles to use RDP for accessing remote computers.
Get started using Remote Desktop with Windows XP Professional
Understanding the Remote Desktop Protocol (RDP)
You should have VPN access or your computer should have static IP for using RDP.
If you are not having static IP, you can use TeamViewer for achieving the samething (i-e accessing remote machine thro' Internet)
You can download it and use it freely for non-commercial purpose.
You can use either automatically generated number or registered user id for identifying and accessing the remote computer.