Exit the Steam client application.
Browse to the Steam installation folder (C:\Program Files\Steam by default) for the Steam installation you would like to move.
Move the steamapps folder from the Steam installation folder to your desktop.
Review the Uninstalling Steam topic for instructions to uninstall Steam (this must be done to remove your old Steam installation settings from the Windows Registry).
Review the Installing Steam topic for instructions to re-install Steam to the desired location.
Move the steamapps folder into the new Steam installation folder to copy all of your downloaded game content, settings, and saved games to the new location.
Start Steam and log in to your existing Steam account to confirm that the move was successful.