How do I get my Nissan Almera stereo to work?

The prev owners took the battery out while they weren't using it. When they put the battery back in the stereo stopped working. The code doesn't work, but we've heard that if you drive the car around for an hour the radio should reset and work again.

If I can't get it to work I would like to replace it, but removing it would be another problem.. Where do I start?