Gourami presents a free tool to uninstall every version of a ICA client from a Windows 2000 or Windows XP Workstation. It's given the name UNICA!
How it works:
When started with the correct command line options, UNICA searches the uninstall information of a workstation for every product which was released by Citrix and uninstalls it. UNICA waits till everything is finished uninstalling, and then launches the installation command line for deploying the new client.
This is a ideal tool when you have several different versions of the ICA client installed over several different workstations. This is also a great help if you have 2 or even 3 versions installed on the same workstation. UNICA automatically detects and uninstalls them.
Because UNICA uninstalls every product that is released by Citrix, it also uninstalls the presentation server console, or even presentation server itself. Therefore a safety is build in, UNICA is made not to run on Windows Server. But it is still recommended to not run UNICA on windows XenApp/Presenation servers.