error al activar un tema

saludos resulta que instale un tema que descargue de la pagina oficial de drupal y al activarlo me salio esto en la pagina principal y resulta que no puedo hacer nada ni se como revertir el cambio... me da vartios erros de este tipo

• Warning: include(C:\wamp\www\drupal/sites/all/themes/tb_sirate/tpl/page.tpl.php): failed to open stream: No such file or directory en theme_render_template() (línea 1517 de C:\wamp\www\drupal\includes\theme.inc).
• Warning: include(): Failed opening 'C:\wamp\www\drupal/sites/all/themes/tb_sirate/tpl/page.tpl.php' for inclusion (include_path='.;C:\php\pear') en theme_render_template() (línea 1517 de C:\wamp\www\drupal\includes\theme.inc).
• Notice: Undefined index: nucleus en drupal_theme_initialize() (línea 98 de C:\wamp\www\drupal\includes\theme.inc).
• Notice: Trying to get property of non-object en drupal_alter() (línea 1080 de C:\wamp\www\drupal\includes\module.inc).

Fatal error: Call to undefined function nucleus_group_class() in C:\wamp\www\drupal\sites\all\themes\tb_sirate\tpl\page.tpl.php on line 191 Call Stack #TimeMemoryFunctionLocation 10.0004250568{main}( )..\index.php:0 20.289316912984menu_execute_active_handler( )..\index.php:21 30.623017565672drupal_deliver_page( )..\menu.inc:532 40.644017566920drupal_deliver_html_page( )..\common.inc:2563 50.644217568536drupal_render_page( )..\common.inc:2675 61.184117940656drupal_render( )..\common.inc:5754 71.184217942960theme( )..\common.inc:5892 81.210117981744theme_render_template( )..\theme.inc:1201 91.211318092336include( 'C:\wamp\www\drupal\sites\all\themes\tb_sirate\tpl\page.tpl.php' )..\theme.inc:1517