[dsio]

just looking at the picture i think the top panel is just about the only panel on that computer that *is* steel. theres a pretty easy test. grab a fridge magnet. aluminium is a non-ferrous metal, where as steel isnt. The magnet will be atracted to the steel and will not be atracted to the aluminium.

that is the easiest way to find out. With the case being that cheap i doubt its aluminium on top, as it would need steel for structural integrity if nothing else. good cheap case though.

if its aluminium happy cutting, but watch for buckling and warping. also beware as often aluminium is covered with a plastic kind of coating over the anodisation which resists scratches, but also catches fire when your hole saw gets too hot. Particularly thermaltake cases are like that but some others do too.

If its steel, make sure your local hardware store has a good supply of drill bits. Because you are going to need them on tap LOL.