I have the same issue.
DV9700z with AMD Athlon 64 (X2) and nvidia graphics card running Vista.
My optical drive "disappeared" first 4 weeks ago. I could not get it back. Tried to install a new optical drive, same issue, device manager cannot see it. 3 weeks later, my HDD "died". Cannot boot windows. I see the HP invent welcome screen, then "No Operating System found" msg. I know the HDD works because I tested myself and just to make sure, had it tested.
With this configuration, it is a known issue that the MB gets fried by the overheating of the graphics card.
HP wants $400 to fix the issue and they say it's the MB.