I recently bought i secondhand laptop, a HP Compaq NX6110, from a company who updated they're computers. The IT-dude said the administrator password to the BIOS was lost, but since it booted from USB and CD-Rom it should be no problems. When at home, I started it up and love and behold Windows XP started up in all it's glory... As I don't have laptop running linux, Ubuntu seemed like a good way to go.. The laptop booted the LiveCD with no problems, so installation where the next logical step. Installation went without a problem, and so did the first reboot. So far, so good. Not even a slight little hint of trouble. I finalized the installation, adding all my additional software and uset the comp for a couple of days without rebooting. But then...a reboot was required, and the computer was about to leave me. After reboting, as I'm leaving the BIOS, all I get is a message "No system disk or disk error", the CD-Rom is unavailable, but USB boot still works.
Booting a livecd from a external cdrom works, but no HDD is recogniced anymore.

Resetting the BIOS to bypass the admin password seems difficult as removing the CMOS battery did nothing.

Any hope of regaining access to this computer, other than sending it to HP?
The price of a service is most likely more than I payed for the comp so i'll rather by another than sending it in.

Sending it in certainly isn't an option, the prices (as you guessed) are insane.

Reseting the BIOS password may require shorting two contacts on the board instead of just removing the battery. If there are no contacts or jumpers to clear the battery, then take out the CMOS battery (pull the machines main battery and AC, obviously) and then try to turn the machine on while it is out. Sometimes the latent charge that the motherboard holds is enough to sustain the BIOS, so trying to turn it on should drain it completely.

As for the actual HDD issue, that is a hard one. You can't detect anything at all when booting to a live CD? Not even the physical drive (don't worry about detecting partitions and filesystems yet). There is really nothing you can do from the software side to make a drive completely drop off like that, so there could be a hardware issue. In fact, make sure that the IDE controller is not disabled in the BIOS (though I don't know how that could happen without you doing it yourself).

No jumpers that i can see...and allready tried to power on without the cmos battery.. however, I'm suspecting that it's somekind of data protection system enabled, that have disabled access to any optical drives. Found a pdf from HP that mentioned sutch a system on some laptops.... I'll ask the admin that sold me the computer to go have another look for the password, as it seems vital to get this computer running again.

Download Hiren's boot disc. You can burn it to a CD and boot from that. It contains a DOS (gasp) based program that can reset the BIOS password for you. I've needed this many times and it works like a charm. I can't remember the exact program, but it's included no the disc. The site for Hiren has a list of programs. Should be easy to point it out.

Brandon

edit: As for certain drives not being accessible, you may want to look into an intermittent IDE connection. Make sure the drive is firmly set (not too hard, obviously). It sounds like you've opened the case already and may have jarred something loose.