If you don't have the disks that came with the computer (or if it didn't come with any) then you will have to order it from Acer. What is happening here is that the computer is looking for something to boot to, going through the boot order, not seeing anything, then coming to the network device and trying to boot using the network. Since your network doesn't support it, it exits the utility, sees that you don't have a boot device, then gives the error "no bootable device..." This is normally caused by a hard drive going bad, so even if you did get a boot device it would fail to install since the drive is most likely bad. To fix this issue, you'd want to replace the hard drive and use either the recovery media that you ordered from the manufacturer to install Windows or use a copy of a Windows install disk and the key on your computer to activate it.