How do I remove these brackets?

[soopcan]

Hi, I'm pretty new to pc building as a whole and my sibling gave me a 650ti that he never used, so I decided to put it in my pc. There are 2 brackets that are easily removed with 1 screw but there are 2 others that don't seem to be able to be removed, since I don't see any other screws. The unremovable ones have an engraving of a screwdriver in them though. Any help?
The case is from an old HP Pavilion p6-2327c

Here are some pictures of the brackets:
http://imgur.com/Tk2e68M
http://imgur.com/eflcHM7

 

[alexoiu]

Hi, You'd remove them with a screwdriver, or similar. There are small joints that you have to break.

 

[the_crippler]

Yeah, like the person above said, they're connected, but are meant to be punched out.