Did you try to locate php.ini and do this?
;extension=php_mbstring.dll
;extension=php_mcrypt.dll
The semi-colon in front of these lines comments them out. Delete the semi-colons, save the file, then restart your web server. Then try phpMyAdmin again and see if you are still getting errors.
This is from google so try it and if it doesn't work just undo what you did.