We picked this very generic topic today, because in past we have seen lot of generic queries around the same.Without going to specific questions, we would like to share few points about Adobe Photoshop Elements, which may help you in answering your question related to installation/use of various versions of Adobe Photoshop Elements on same computer or Mac.
1. Technically, there is nothing like Upgrade in Adobe Photoshop Elements. Whenever you try to install newer version of Adobe Photoshop Elements, it's installed and earlier one is also kept on your computer.
2. All installed versions of Adobe Photoshop Elements can be used on your computer in following manner :-
a. All Organizers can be launched and used at same time.
b. At any point of time, only one Editor can be launched. Which means that if you have PSE 8, 9 and 10 are installed, at any point of time you can only launch either 8 Editor, 9 Editor or 10 Editor.
c. If you want to open Catalog from old version to new version, you need to convert the catalog first. It ill create new copy of Catalog for your newer version.
3. Make sure that older version of Adobe Photoshop Elements is not launched on your computer, while installing newer version.
4. In case, you don't want multiple versions of Adobe Photoshop Elements, you need to uninstall the versions you don't want.
5. All versions of Adobe Photoshop Elements can be installed independently. Which means that sequence of installations is not very important. You can choose to install Version 10 first and then version 7.
6. Any installation of Adobe Photoshop Elements, doesn't uninstall anything from your computer. This is one of the very common assumption when folks install newer version on top of older one. So e.g.- if you install PSE10 on top of PSE7, nothing will happen to PSE7. Finally you will have PSE7 as well as PSE10 for use. If you don't want earlier version, you can choose to uninstall PSE7.
As of now above points came to our mind and we shall kep this list updating.