General

@Kingzer Your description of the symptoms sounds like classic overheating.
Visual artifacts and BSODs can be caused by a dead or clogged fan on the video card, and general overheating/shutting down/rebooting can be caused by dust in the CPU fan and heatsink.

You should open the side of your desktop about once a year and check the fans for dust clogging.
I found this picture that's supposedly your computer's motherboard, if it's not exact, it should be close to what you'll see inside.

Take the left side off (when facing the front of the computer) and use a flashlight to look closely at the two areas indicated by the red arrows:
http://dl.dropboxusercontent.com/u/26443090/Gateway%20Motherboard.jpg

#1 is the CPU fan and heatsink. The silver aluminum fins below the black fan blades should look just like in the picture, with no gray dust bunnies or blanket on them.
If you see gray dust all over the fins, you should use "canned air" (from a computer store) to blow the dust out until it looks like the picture.
You can also (VERY CAREFULLY) remove the fan and use a brush like an old toothbrush to brush the dust out of the fins.

#2 is the Video Card fan and heatsink. You can't see it in the picture because the video card sits perpendicular to the motherboard (it sticks out of the motherboard) and the fan and heatsink are on the bottom side of it. Lay the computer on its other side so the open side is facing up and use the flashlight to look on the bottom side of the video card. Again, the fan and heatsink should be free of dust. If not, use the canned air to blow the dust out of the fan and heatsink fins. It's more difficult to remove and replace the fan on the video card, so don't try to do it.

Also, briefly turn the computer on while it's lying on its side and with the flashlight make sure both the CPU fan and the video card fan are turning when the computer is on.
If the video card fan doesn't spin, or spins irregularly, then the fan, or more likely the entire video card should be replaced.

[quote=ApplesAreOkay]try cs go[/quote]

It would be hilarious if this fixed the problem.

[quote=ApplesAreOkay]try cs go[/quote]

same thing, even if i watch some videos. most videos i don't have my computer restarting on me tho

try cs go

[quote=Killeem]@Kingzer: i suck ass with computers but from my own experience with my comp, it never shut off when it came to browsing the internet, only when games are being played. game could be using more memory or w.e causing it to overheat then? idk man, try it just for the hell of it if you're desperate, who knows it might even work[/quote]

hmm sounds sketchy like i don't want to use a fan whenever i play games and idek if it's the problem lol. yeah i used to leave my computer on all the time when i sleep but it just hibernates so idk

@coldair nope i didn't put anything or add anything to my computer

have you put any more ram in the computer yourself? if so make sure its compatible

@Kingzer: i suck ass with computers but from my own experience with my comp, it never shut off when it came to browsing the internet, only when games are being played. game could be using more memory or w.e causing it to overheat then? idk man, try it just for the hell of it if you're desperate, who knows it might even work

[quote=Killeem]my comp had a similar problem i guess. i keep my comp on 24/7 so now its crap, but whenever i try to play games like combat arms or league, my computer restarts / shuts off on its own.
all i have to do is place a fan near my comp to cool it off so it doesnt restart / shut off on its own.
try that and see if it works?[/quote]

i don't think it's overheating though because my computer doesn't feel hot and my fan isn't too loud when on the computer, but just speedens up a little more when playing games

also how do i check my dust filters and stuff? do i have to take my computer apart?

Most BSOD is heat related.
My computer BOSD and i flipped out becuase i keep my Pc software updated and pristine.
Then i checked my dust filter, more dirty then a drunk blonde

my comp had a similar problem i guess. i keep my comp on 24/7 so now its crap, but whenever i try to play games like combat arms or league, my computer restarts / shuts off on its own.
all i have to do is place a fan near my comp to cool it off so it doesnt restart / shut off on its own.
try that and see if it works?

@Kingzer like maybe you installed a corrupt graphics driver.

Edit: are you sure you are using a NVidia video card because on the gateway website I also found an Intel and AMD drivers

it's not an old computer though, i'd say like 3 years old? it's a gateway and i think i did install the right drivers. any ideas on how to tell if i installed the right graphics driver?

my computer stays relatively quiet too, but when i start a game the fan will increase speed and you can hear it a little more, but when i freeze the fan speedens and is decently louder for like a couple seconds and then my computer restarts

edit: it's a gateway dx4850 and windows 7

BSOD is hardware and driver related maybe you haven't install the right graphics drivers

Edit: if I may ask what PC model you got?

I can think of a number of problems happening with it: overheating, outdated processor, dust in the fans, etc.
But since you wouldn't really know how to fix any of those, I suggest just buying a new computer altogether.