I get an AJAX error when I install Drupal 7: Why?
The problem is the  maximum execution time being exceeded. To fix this, you should change the maximum execution time in your php.ini file. Click on the Wamp icon on the taskbar, select PHP -> php.ini, find "max_execution_time" and change it from 30 to like 100-300, to make sure even the slower scripts get their job done before the timeout.

Remember to restart the server after you change the settings.