I agree with you on not wanting to throw away working hardware.
First issue, booting from the CD (?) and continuing from HDD requires you to know where you installed to. The default install is to "/dev/sda1", but it could be different. If you're sure you got that entry right, then the installation is corrupt.
It would not be unusual for an old optical drive to not work reliably all the time. A fingerprint on the disc can be enough to confuse it.
I'm not familiar with the technical term "petunia", but I assume you installed using the text installer, by typing "install" on the first screen?
The installer needs at least 256M of RAM and 4G of hard drive space, are those specs met?