Error MSFTPSVC ID 100

Hi, I am gettingthe following error in my “Event Viewer:
Source: MSFTPSVC
Category: None
Type: Warning
Even ID: 100
Description: “The server was unable to logon the Windows NT account ‘ADMINISTRATOR’ due to the following error: Logon failure: unknown user name or bad password. The data is the error code.”

Someone knows how to solve this problem?

Thanks
cattana