As another option you can zero out the install condition on the components you want to remove and set the flag to re-evaluate install conditions. This will allow you to perform a minor upgrade and still remove components from the installed system. The installer will still have them but will remove them from the system if it detects them. If installer size is a big concern you can add dummy place holder files that are empty and have the correct names. The GUIDs will HAVE to match though in order to pull this off.
So if you needed to keep the new guids you could add a second component with the old guid and then follow the steps i mentioned above to remove it and use only the new one going forward. This is likely your only other viable option if you have already released a version with conflicting guids and want to be able to upgrade and support both from a new installer.
so using your example:
Setup 1 had Component ID : {9E5018E0-5707-4B03-A937-B4DA13BA7E1B} is lets say version 1.0
Setup 2 has Component ID : {21741DCA-DDEC-48AC-9CBC-EE458DC0E063} and this is version 1.1
you are creating setup 3 that is version 1.2 and you want to be able to install over both setup 1 and 2.
As such you will need a component with the same files for each GUID.
setup1's guid will be your dummy guid. set the install condition to 0 and flip the re-evaluate condition to 'yes' and add all the files that were in the component in setup 1 (version 1.0)
Setup 2's guid will be your component going forward. so add another component with this guid to setup3 with all the files that are in setup 2 (version 1.1)
this should allow setup 3 to properly perform a minor upgrade over setup1 (assuming you didnt violate any other upgrade rules). by removing the old component and dropping the new one in its place.
this should also allow a minor upgrade over setup2 as the component id should be the same. One of the posts on my old account has some really helpful information from Stefan about this. Ill see if I can dig it up.
edited for clarity
Edited by overlord, 19 March 2014 - 14:43.