Application event log windows 2003

Hi All,

Can someone please intrepret for me what this is saying and if possible suggest a solution so that it is removed:

on windows 2003, under event viewer > application, the following message is displayed:

Type failure audit.

Source: mssqlserver
computer: edd-sql1
event id: 18456
Description
Login failed for user ‘EDD\EDD-CITRIX8$’. [CLIENT: 10.21.9.39]

the user EDD-CITRIX8$ is not in our active directory!

All help will be greatly appreciated:)
Kay