I was just wanting to spray my case black and someone told me that if the inside is not "grounded" something could quite possibly short out and/or fry. Just wondering if this is true and what type of spray paint I should use etc. My system is an Intel Core 2 Duo, ASUS P5KPL-CM mobo, Gigabyte 720W PSU etc.
What they are referring to is that the case is typically used as the negative (earth) ground for the motherboard. If you spraypaint, there is a possibility that the screws that go through the motherboard won't actually get a good bite into the case metal and the motherboard will not be electrically grounded. This can cause all sorts of strange errors to occur. Tape off ALL the screw holes in the case, especially the power supply, so that they don't get painted and the area immediately around them don't get painted and this should eliminate that. You will also need to make sure to do similar for the slot cover area since some boards may ground through their slot covers.
The other issue is to make sure that the paint is thoroughly dry - when you power up, the heat may bake some of the volatiles out of the paint. Don't really think you want to be breathing that stuff.
The case is NOT grounded, it is NOT electrically connected to the motherboard via the screws that attach the motherboard to the case. The case prevents the electromagnetic fields from causing interference, but it does not need a connection to the powersupply (or motherboard) for that. You can safely paint the case.
Clean the case with degreaser (white spirit or ammonia), dry well and then spray with automotive paint or any paint-in-a-spraycan. For a really nice job you should spray a primer first, very lightly sand it when dry and then spray the final color.
If you've never spraypainted before practice on a test piece first. Basically you don't want to start spraying while pointed at the object. Start spraying next to the object, then move over the object in a fluid motion, continue until you are no longer spraying on the object and then stop spraying. Spray slightly overlapping strokes.
It's better to apply several thin layers than one big droopy mess.
Work cleanly and neatly, pay attention to what you're doing and nothing will go wrong. It is easy, once you get the hang of it.