I can sympathize because I'm almost in the same position. I have an
old laptop that won't boot from a USB stick and had a non-functional
DVD drive. I found an exact replacement in Singapore for the broken
DVD/CD drive in the mail this week and I know it will boot from that
because it did before.

But before I ordered the new DVD I looked for some way to start an
installation without using an external device. I know I once had a
utility that allowed booting an .iso on the hard drive, but I couldn't
find it. Whether that could be used to install an O/S I don't know.

Anyone have ideas?