|Have you created the recovery DVDs or CDs ? You may copy and re-record the second disk using another DVD/CD writer and try again.|
If still they do not work, you should contact Acer for spare Recovery disks for your system. You may have to supply proof of purchase, though.
DVD/CD storage conditions are critical to the reliability and life of the DVD/CD disks, such as temperature, exposure to direct sunlight, position of disk placement, etc..