Uninstalling 4.0 is done by uninstalling CiscoWorks from the VMS server. Both CSA 4.03 and CSA 4.5 are available to uninstall, therefore choosing 4.03 will allow you to remove 4.0.
Removing previous versions or rules/policies/kits, etc, can just be deleted from CSAMC by selecting them and deleting. There is no uninstall for these.