Andrei - if you don't see the ActivInspire - Studio header, as shown in the previous answer, you may be able to view the Dashboard > Configure.. and select the box "Launch next time using the Studio look and feel.."
OR the Primary look and feel if you are working with younger children.
When you close and re-launch ActivInspire the interface should no longer be the PowerPoint version.
Let us know if this works?