Here is how I opened up the case this last time, which is much easier than my previous attempts at it.
Disclaimer: I am not suggesting that you do this, I did it merely for curiosity's sake; if you were to try to do this the device may break, warranty voided, or any number of bad things could happen like fires or damage/death to yourself or other items or persons, etc for which I am not, and you agree I am not, liable. Note that manufacturers sometimes change their case designs as well.
- I unplugged the power
- Removed the smart card from the front so I didn't accidentally break it
- Removed the visible screw on the case's bottom
- Pried off the rubber pad on the case's bottom which is closest to the green and yellow RCA jack and unscrewed the screw underneath
- Pried off the rubber pad on the case's bottom which is diagonal from the one just pried off and unscrewed the screw underneath
- Looked in the slots on the bottom of the case with a flashlight to see that an object could be stuck in them and bent slightly to unlatch, except for the three inner slots with green circuit board visible which can be ignored
- I unbent four medium-thickness 1.5" (2" long measured with a ruler) cotter pins, the kind obtainable from a hardware store, to a 90 degree angle
- Inserted one end of the cotter pin straightly into either one of the two slots closest to the back of the case, to the point where it stopped on its own [Update: click here to see tzdvl's drawing of this step
- Carefully applied sideways pressure (relative to the case) to the cotter pin so the part of the cotter pin outside the case moved away from the case and the part of the cotter pin inside the case moved toward the other rear slot
- At a certain point while bending the cotter pin sideways and applying slight downward pressure, the cotter pin slipped farther into the case. I let it slide in a bit more. This unhooked the latch in the slot and allowed me to remove my hand from the inserted cotter pin during the rest of the steps.
- I repeated this with the other three slots using the other three bent cotter pins. Noted that the slots in the front only allowed me to insert the cotter pin slightly past the point where the cotter pin stopped on its own.
- I inserted a flathead screwdriver in between the top and the bottom of the case at the closest corner to one of the back cotter pins
- Twisted the screwdriver at the corner to pry the top and the bottom of the case apart slightly but not enough to damage the case
- At the same time, with my other hand, used another flathead screwdriver to unhook the closest of the two tabs on the rear of the case. That corner of the case now opened up farther
- Removed the screwdriver from the corner of the case
- Inserted the screwdriver slightly to the outside of the tab that the other screwdriver is in, and used it to pry apart the top and bottom of the case just to the point where the screwdriver fits in between the top and bottom of the case
- Removed both screwdrivers, and noted that the top and bottom of the case remain somewhat separated
- Repeated the last six steps with the other rear corner
- I separated the top from the bottom of the case at the back of the case with my hands, without much effort, and noted that this caused the front of the case to also separate
[- Update: click here to see tzdvl's drawing of an idea to make the case open easier in the future with package sealing tape
Here is a picture of what the underside of my case looks like, and a cotter pin I previously used, though the cotter pins I used this last time are a slightly different size, noted above. This picture shows the two round screw holes in the bottom-left and top-right corners which were under the rubber feet on mine. The other screw hole is in the top-left of the picture which looks like a semi-circle indent in the edge of the case by the rubber foot that is by the power cord. The rectangular slots that I used the cotter pin on to carefully unlatch my case are the four non-green ones.