Remote Desktop requires XP Pro on the host system. If you can’t get it to work, make sure port 3389 is approved outgoing and incoming. If you’re accessing the system from outside the internal (LAN) network, you need to forward port 3399 to the desired computer you want to access. If you can’t connect even after all that, it’s probably a firewall or router issue. Remote Desktop can be stymied by these. Try the free LogMeIn at logmein.com – it uses a central server to avoid router configuration issues.