HELP! serious issues with my computer, any input apriciated

i play 3-d mmorpg games alot, and one day, i was playing one of my favorites, and all the sudden the screen froze, next things i know the screen went black, than started flashing CRAZY colors, and crazy patterns consisting of an assorted array of lines, and would switch crazy colors and line formations randomly, at first this only happend when i would try to play this game. i talked to dell support, and they said it was the game, i was thinking it was the graphics card. well i listened to him cause it only did this in that game, but then i tried a few others to see if it really was that game, well every other game i tried, it did the same thing. the dell support team is just incredibly idiotic, i kept getting switched from one team to another with out any answers, the hard ware department told me it was a software problem, the software department told me it was a hardware problem. and while this whole thing was going on, i kept saying it was a graphics card problem, well soon after i got no were with dall, and stoped calling. my computer started doing it randomly weather i was playing a game or watching a video. now i cant get on longer than 5 minutes without it freezing and giving me crazy colors. half the time when i try to rebot, i get the same crap at start up before anything comes onto the screen. i have to restart my computer like 4-5 times before it starts up correctly. i though it MIGHT have been my monitor, so i tried 3 others. same crap.so now what i wanna know is, is it my graphics card thats causing these issues, or could it be something else. also if it is a graphics card problem, what should i replace it with. ive done some research on cards, but idk what would be best for watching loads of videos and playing games like, asda story, comand and counquer 3 when it comes out and WoW, that wouldnt kill the money in my wallet. i have a dell insperon 530 with 2gb ram, a intel core 2 duo processor, and a 500gb hard drive, i think the current graphics card is a nvidia 8600 gt, not completely sure tho, your help and insight into this issue would be much apriciatetd, sorry for the grammer and spelling issues, im trying to type this before my computer goes hay wire again.

they bsed me for a week until my warrenty ran out, now they want 150$ for a year extension on my warrenty, i talked to management and they were as inept as the staff, rather use that 150$ for a new graphics card rather than a warrenty extension, which will only get me a replacement on the crappy graphics card i already have, and thats IF they want to. they didnt seem to keen on the idea when i last talked to them, in fact one of the managers hung up on me -_- cause i was getting pissed from getting the "run-around" all i want to do now, is figure out what the problem is.

did you check to make certain that the card is properly seated and connected,if so then replace it.also check your ram also,check all your connections,i had a hdd go south on me once finally found out that it was not connected firmly to one side of the ribbon cable,douh!!...