Hi David,
Glad to hear that you have the cover off.....To unlatch the hard drive, you need to remove the screws like you've already done. Then on the opposite side of the drive mounting (closest to the outside edge of the case), there are two latches down low that have to be released. You should be able to see two slots or holes down low on the lower outside edge of the drive mechanism. I usually stick a small screwdriver or something pointed in there to push in and release the latches so the drive assembly can slide and release....That should do it, please give it a try....

Randy