You wish to give users the option to quickly ask a question about a particular product then this simple extension will do the trick. This will present the user with a contact form with the product in question liked to at the top. You can download extension from here
Install the extension in the normal manner. To add the question you will need to edit your product page. Add the following where you wish to code to appear.
<?php if(Mage::getStoreConfigFlag('productquestion/productquestion/enabled')): $url = $this->helper("productquestion")->getAddUrl($_product); ?> <?php echo $this->__('Ask a question about this product') ?> <?php endif; ?>