New HDD & OS, New DVD Drive Not Reading Disks

Hi,

My problem is that the DVD/RW Drive on my HP dv6700 is not reading discs. To catch everyone up, I decided to make some upgrades to the laptop rather than buying a whole new computer, and the problem with the drive not reading disks has stopped me in my tracks.

A few months ago I learned that I needed to replace the HDD - the computer wouldn't start up no matter what - it was dead. So after I decided I didn't want to buy a whole new computer, I bought a new HDD and bought Windows 7 (upgrade from Windows Vista that it had before). The other problem was that for a long time before the hard drive went out, I always had problems getting disks to read on the DVD drive. I tried cleaning it etc. but nothing worked, so I bought a new (used) one of those too.

I replaced the HDD and DVD drive, then when I put in my new disk for Windows 7, the replacement DVD drive is not reading the disc for the OS - the computer keeps telling me "Operating System Cannot be Found".

I'm posting here because most fixes I'm finding online approach the issue through the OS, which I obviously don't have on my computer. Is it possible that my new (used) DVD drive is already broken and I just need to buy another one? Hoping it would be an easy fix, I already tried cleaning it (carefully so as to not damage the laser) and moving the transport mechanism as another post suggested on this website. I also went into the BIOS and made the DVD drive #1 in the boot process. None of this has worked so far.

I'm stumped and would be grateful for some help in finding a solution!