is my video card done?

okay, the screen kinda flicks, wherever I put the cursor goes from black squares to a few coloured squares, whatever I was trying to open, like applications so I could get in and run a check, just opens in a black box. I can' t see anything. I have some of the top line, some of it does not come in so I have to push and hold to shut down and restart. I have done this several times, letting the whole thing "cool off" not that the mac is giving off heat, just a thought.

Everytime I start, my mail comes in, that I can see just fine, anything else just opens in a black box and I ahve tried waiting to see if the box would come in, but after an hour the last try, all I can get are still the black boxes so I can't see what's in the box. I am just wondering if this sounds like a hardware problem or a hack job.

thanks,