Windows Server 2003 SP2, SQL Server 2000 SP4 (8.00.2039 - according to Add/Remove programs) but with patch 8.00.2055 applied according to 'select @@version'
When I try to apply the cumulative update 8.00.2187 the 'Instances to update' dialogue box in the wizard does not select anything and does not allow me to select anything. If I select 'next' I am told that I haven't selected anything.
When I installed 8.0.2187 directly to 8.00.2039 on another server there is no problem.
Do I need to remove 8.00.2055 prior to 8.00.2187? If so, how do I do that? Or it there another way to 'force' 8.00.2187 to install?
No you don't need to remove the 2055 patch. Removing specific patches isn't supported on SQL 2000.
Try restarting the instance and see if that helps. The version that is returned by @@version is the correct version.