To make a window without seeing those tabs, you're basically left with cutting them off. Then, get a window larger than the hole and mount it inside such that the mounting hardware is out of sight.
The easiest way of doing this is to drill holes in the case and window. Then, just bolt it. Of course, you don't get the clean look on the outside this way since you've got exposed bolts.
Without seeing the rest of the case, it's hard to say what else would work. I'm against using ghetto methods such as tape