To minimize the annoyance, make sure that A2010 is the default and always open apps with that version. Then if you specifically want to test with A2007, open A2007 and then open the app.
Behind the scenes Access is fighting with itself over control of the registry. Each time you open a different version of Access it takes over the registry and that is the installing.............. message you see. Just stick with A2010 and you won't see the message except for the times you actually need to swap versions.