You don't need to uninstall Vue 4. Vue 4 and Vue 4 Pro are very different standalone programs. On both machines you just need to keep or to reinstall render cow. I have on my machine Vue 2, Vue 3, Vue 4 and Vue 4 Pro (the old versions are there to be able to answer questions to users who are using them) What I did when Vue Pro came out: I made a copy of Vue 4 (from drive E) to another drive (F) and installed the sidegrade over the copy without problem. I just had to write manually a sentence in the Vue Pro.reg when I installed Mover 4. It did not want to "update" the reg file, I don't know why. BTW I never install any important software on drive C where my Windows is (XP PRO), because if ever I need to reformat C, I can keep save my software (VUE) files:-)