I have been meaning to post my pictures for a while. Thanks to those that helped me accomplish it (anleva). These are of an HR-24-100.
In picture #1 unscrew the two screws in 0 that hold the drive down (don't worry there are two more inside, these are a standard t-10), then release tabs 1,2,3 and gently lift up on the coax terminal (this was the easiest way I found). Place a screwdriver underneath the top like in picture #2. The tabs_closeup picture shows the outside case where you need to insert the flat blade and circled in blue the tab that you need to push in to release the top of the case.
Release tabs 4,5,6 in picture #1. Elevate the second side by using a flat screwdriver like in picture #3
The top is now clear like in #4 and will slide straight off revealing picture #5
Place new drive on top of old drive like in picture #6 and boot up and format like all the other drive replacement threads
Remove the two drive screws in picture #7 with the t-10 screwdriver. The old drive should now come out.
Replace with new drive, attach drive screws, plug in cords, place top back on and slide until it clicks and you are done!
Overall, once you figure out the tabs (and it is really easy) this DVR is a ton easier than the hr-20,23
Why did you put the HDD on top of the old HDD and reboot?