PortNumber (Default Value 00000D3D, Hex for (3389))
Enter the new port number in Hex.[/code:1]
IIS (Presuming Windows 2003)
[code:1]IIS can be done within the IIS Manager
expand to the website (usually Default Website)
Right Click --> Properties
The first tab (Web Site) has the TCP Port, just change this value and restart the website.
Its worth noting that although it can help deter the attack, it will do nothing about preventing it. Its not that difficult to fingerprint the services/port to see whats actually running on them.