Nvidia GTS 250 crashes and heating issue

Hello everyone, now this might be a bit long because I want to give you guys all the proper information. My PC is quite old, at least 4 years now and I have been upgrading it and it has performed well. Last Monday I upgraded my crappy 9300 gs VGA to a gets 250. The cards not brand new its used but the guy I bought it from hadn't really played a lot of games and it looked alright. Since my PC is old I had to get a new PSU to power the VGA( my old PSU didn't have a six pin VGA power cable) and I bought a 500 watt PSU which isn't really a good one but the guy I bought the card from recommended it since he used it. Onc I plugged everything in I had to install another nvidia driver for the card to operate properly and I plate Mafia 2 for quite a long time with most of the settings turned up. Then about an hour later mafia 2 started crashing a lot so I loaded up empire total war and that crashed after sometime as well. I went online and found out that the problem might be the PSU or the drivers or overheating so I first did a full system format and installed an older driver which users on the net said were more stable. I then got evga precision and ramped up the GPU fan from 35% to 95 %. I know the fan sped up because I can hear it buzzing away. I then installed and loaded up Witcher 2 enhanced edition and it crashed about 45 minutes I to the game. It was getting late and I was sleepy so I shut down and was putting the side cover which I had remove to plugin the GPU when I noticed the inside of the PC was warm. So I touched the VGA and the circuit boards components were burning hot.... Strangely though evga precision GPU temperature even while playing was never more than 60c but I also understand that it only measures the GPU temperature and not anything else. The next day I couldn't use the PC. Yesterday I loaded it up and played witcher for more than two hours with ought a single hitch and then the crashing started. Today also I couldlay for more than two hours before it started crashing. At all these scenarios the common occurrence was the VGA being very hot but the GPU itself only peaked at 64c and I checked online and it was not that bad. I am now at a point where I believe that its the VGA overheating that causes these issues. Even with the side cover off the temperature inside the PC is quite warm and the VGA 's little circuit components can bien a finger if you touch it and hold for a few seconds. The moment I turn off the PC the VGA starts cooling obviously and it works fine for some time. My PC case is quite old like I said and doesn't really have much cool in. The PSU I bought has a massive fan but that's it and I know this is the reason its heating up. So my question is whether the issue is with the heating or is it something else? I can fix the heating by getting a better case I suppose. My system specs are as follows

Core 2 duo 4500 2.2 ( I have slightly over clocked it without any increase of power to 2.7 but that was two years ago and it runs fine)

3 GB ddr2 ram

G31m+ motherboard.

Thanks for taking the time to read through all of that

Edit: just read about artifacts and I must add that when playing mafia 2 there was a strange occurrence when the game sort of split screened and one side was blue before it crashed... Is that an artifact?