Greetings. The model is Aspire 5742z. I have the UUID, serial number,SSNID, and other product info if needed. The HHD is a Western Digital black, 320 GB. The O/S that was loaded on the computer was Windows Vista, which I assumed to be the best one to use as a replacement. When trying to diagnose the problem I ordered recovery material from Acer. This consists of one system disk, 3 recovery disks, and one language disk. These did not work with the old hard drive so I assumed the hard drive needed to be replaced, which is what I am doing now. Can I use these disks to reload the O/S? I have no other disks from Acer.