Cannot boot from CD or external USB

[Thomas Blasejewicz]

Good afternoon
I do have an old HP nx9005 laptop, used exclusively for "experimenting"
with Linux.
Currently: Ubuntu 12.04 LTS (installed from CD)

due to the limited hardware I would like to install Lubuntu 14.04
However:
* when the live CD is in the drive, the PC does not read it at startup
and boots "normally" from HDD
* doing so, it often sounds a terribly loud alarm, something I have
never heard from a computer before.
* booting from HDD and inserting the CD later -> "Software Packages
Volume Detected" is displayed
and the Package Manager starts .. but that is it. I cannot run the CD
* connecting an external DVD drive (USB) -> same thing
* sometimes I get a whole "flood" of error messages (which I do not
remember all)
* when I try Ctrl+Alt+delete or something like to do a forced new start,
I get a GNU Grub something screen, but here, same as the next item, I
cannot choose anything.
Just waiting for something to happen "automatically" does not help,
since nothing further happens
* when I try to call up the BIOS or Setup menu, I DO get a number of
options for each
AND and move between the individual items up and down with the arrow keys,
but the Enter key does not work, so I cannot choose anything.
* If 12.04 somehow boots and I can start any software, the enter key
works normally
* Once the O has booted, the CD is recognized = probably meaning the
drive itself is not broken

Question:
IS there a way past all this crazy stuff and set the BIOS so the PC will
boot from the DVD drive?
Or any other way to get in there, delete everything present and make a
clean new install?
Like for example one of those complex commands that you can run in a
terminal?

Somehow I would like to think, that the hardware is still functioning,
but something in the OS has gone terribly wrong.

Thank you in advance
Thomas

(* that machine is in my office; next time I can play with it is
tomorrow afternoon ...)