I have just tried downloading the Moodle 1.7.3 zip file from download.moodle.org, and checked, and all the question type files seem to be in there. Are you getting any error when you try to unzip it?
Quiz
Where have the questiontypes gone???
اس بحث کو بند کر دیا گیا ہے لہذا آپ اس کا مزید جواب نہیں دے سکتے۔