Both, I think.... in Device Manager, I did this:

Right-click on the drive
Uninstall
"Warning: You are about to uninstall the device from your system": Click OK
Drive designation disappears in DM
Repeat for other drive (two optical drives)
Reboot.
Re-open DM to find the same thing as before... namely, three drives (two optical and one thumb) under the DVD/CD-Rom heading [see note below] with the yellow exclamation mark.

** I figured out why the thumb drive is working right. It's actually not... it's a SanDisk Cruzer Micro, which means it does this thing where it creates TWO drives -- one that I know little about but seems to act as a CD drive called U3 and one that acts as a normal thumb drive should, an external HDD. ONLY the latter works... so whatever's wrong on the computer, it really IS affecting all optical drives, including the fake one that this thumbdrive tries to create. In other words, with the thumb drive in, I should have available drives C, D, E, F, G, H, I, J, K and L... D and E are the normal optical drives, G-J are media readers, K is the "optical" "U3" drive, and L is the external HDD from the thumbdrive. Right now, I don't have D, E, or K.

Hope that made sense :-X