What the administration console, the Laserfiche client, and other programs do when they query the list of available Laserfiche servers is to search the Active Directory forest for registered Laserfiche service connection points (SCP). These are objects in Active Directory that describe how to access a particular service.
You need to use the service connection point (SCP) management utility named lfscpcfg.exe in the LFS program directory to remove old SCPs that are no longer useful. This is a command-line program that can be used to delete old SCP entries. Please see the documentation on the SCP utility in the Administration Guide, Appendix C for details.