If you have registered more publishers in replication monitor client tool, you can remove those by renaming\deleting rmsetting.xml file more over deleting each manually.
File can be found in below path:
For SQL Server 2005 Version.
C:\Documents and Settings\<Profile ID>\Application Data\Microsoft\Microsoft SQL Server\90\Tools\SQL Monitor.
For SQL Server 2008R2 Version.
C:\Documents and Settings\<Profile ID>\Application Data\Microsoft\Microsoft SQL Server\100\Tools\SQL Monitor.
For SQL Server 20012 Version.
C:\Documents and Settings\<Profile ID>\Application Data\Microsoft\Microsoft SQL Server\110\Tools\SQL Monitor.
Note : You are Removing only Registered Publishers From Replication Monitor Tool.
