Let's say you installed EB 1.1 into C:\I\like\peaches\RTW. Then you install EB 1.2 into C:\I\like\peaches\RTW. Not C:\I\like\oranges\RTW or C:\I\like\peaches\RTW\EB. The same location.

And run a validation after each 1.2 installation to see if it recognizes its files.