A Magento module that, upon issuing a Credit Memo, will correctly set product availability back to In Stock in
addition to returning the quantity, should the product become Out of Stock when ordered.
Magento Open Source (CE) Version 1.7.x, 1.8.x, 1.9.x
Prior to installing the module, ensure that compilation is disabled.
System -> Tools -> Compilation
Copy the contents into your Magento project directory and refresh the cache.
Within the admin, head to System -> Configuration -> Catalog -> Inventory, expand the Product Stock Options
section and enable the Update Product Stock Availability option.