This shouldn't happen because there are two different applications and they should install properly without errors, however, if the developers used the same registry files, then you will have issues. As soon you finish the installation of one of the apps and then start the next one, it will overwrite the previous registry entries therefore corrupting the registry files.
Another way is to create another use on the same PC, then right click on the 2nd app and select Run As and select the newly created user.
