Windows 7 - Windows 7 won't "see" dual layer discs on DVD Burners

I have Windows 7 Pro 64 bit installed on my computer. It is an HP, and I have 3 DVD drives. 2 are dual layer burners (1 external, 1 internal) and 1 is a DVD ROM drive.

The problem I am having is that the DVD Burners won't "see" dual layer DVD's when inserted, new ones, or ones with data on them (not even the Windows 7 Install Disc).

I first discovered this issue when trying to burn a dual layer dvd in Windows 7, to no avail. I was trying to copy a disc I had previously burned on the same machine when it was running XP. (Disc of Home movies, nothing proprietary or copy protected).

The original was burned on a Verbatim and the the target disc is also a Verbatim.

The DVD ROM drive "sees" the original, but neither of the burners will see the blank disc. I've tried various programs such as nero, IMGBurn and Windows, all with basically the same result. Even when I insert a dual layer disc in either burner (again, blank or with data on it), both the drives just "blink" but nothing happens. If I click on either drive in explorer when a disc is in there, it says "please insert a disc". I've tried waiting for a bit to make sure I gave the computer "time".

I've checked for firmware updates, both drives are up to date. I tried deleting the upper and lower limits in the registry, which actually made the problem worse (the drives then wouldn't see any disc inserted, even CD's or single layer discs).

I am certain the drives are ok (I've connected the external drive to an XP machine and it worked fine), and I'm certain the media is fine (able to play the DVD on another computer, from the DVD ROM drive, or from a stand alone player) and was able to burn a blank on the XP machine.

I've seen countless threads about this issue, but nothing about a fix. Anyone have any ideas?