Since Microsoft stops their support for Windows XP, you should migrate to Windows 7 which Windows 7 can connect to server via remote desktop connection as good as Windows XP. Maybe for some reason the administrator change default port for remote desktop at the server. As Windows 7 user, to enable success remote connection, you have to change the listening port for remote desktop at your Windows 7 that default is 3389 .
Here step by step how to change remote desktop port in Windows 7 :
1. Open registry editor by press [Start] + [r] and type regedit in the form
2. At the registry go to HKEY_LOCAL_MACHINESYSTEMCurrentControlSetControlTerminal ServerWinStationRDP-Tcp
3. Double click on [PortNumber], click decimal and fill the “Value data” with the new port number and finish by clicking OK
4. Quit registry editor and restart the computer to take effect of the change.
If you want to connect to remote computer via remote desktop connection don’t forget to open the new port in the firewall and hope this will make you comfortable with your internet and computer.