I have an Aspire Z3620 all in one desktop from the 2012 run (w/o touch, Pentium G640, 8GB SODIMM memory, 1TB HDD). Some while ago I started getting the message: "Boot disk not detected or disk has failed" after the initial Acer POST screen. Then, entering the BIOS setup, I found that the HDD was detected and set as first priority in the boot order. Consequently I decided it best to run with an external hard drive (Arch Linux on a Seagate external disk). This worked fine for a while, until recently when again I had the error "Boot disk not detected or disk has failed". Accordingly I brought up a fully functional new hard drive tested on another device and a DVD for the recovery of Windows 7. Installing both these (Yes, I checked the cables) and turning the machine on still gave me the same error. Checked BIOS, and indeed the DVD was first in boot order, and both the hard drive and optical disk were listed as devices. The hard drive is functional. Can I have some help to try and boot? I've left the computer sitting unusable for about 4 months as I only now need to use it.