Aspire One A150 Model # ZG5 keeps showing me a Acer screen before informing me that I have a Media test failure and that it has no bootable device. I have no boot disk it asks for, and not sure what is required. Advice?

I solved my problem the old-fashioned way.
With a hammer.

You can reset the Device to original Factory settings by performing the following step:

Reboot your system
As soon as you see the Acer logo, hold the Alt key and start tapping the F10 key.
It will give you a recovery screen and you would be able to perform various recovery process which includes restoring the system to original factory settings. If you restore the system to Factory settings all the data in your computer will be lost.

note: You will be able to access this recovery option only if you haven't changed or Formatted the Hard Drive since it was purchased.

If you need any further assistance in this regards please feel free to contact.

Thank you for choosing Fixya.