One of the great changes of Snow Leopard that has been consolidated with Lion is the arrival -to stay- of 64 bits, already extended almost completely to all Apple applications and many of those made by third parties.
But sometimes it happens that certain driver or software does not work on 64 bits, and if we need it, we can be forced to start in 32 bits, something that is done in a very simple way: restart the Mac and when you hear the start-up sound, press down the «3» and «2» keys.
To make sure, go to System Profile> Software and see if it comes out as in my screenshot.
And then to go back to 64 bits, do we just reboot or do something else have to be done?
I do this and nothing comes up with a poster that reboots the system every so often ……