Is this a new build or is this a new problem that's occurring on a build that was working fine previously? Does it only occur while playing games?
Are you getting a blue screen at all? Any error messages? Beeps or lights on your mobo?
Your first post implied that 50 degrees was your GPU temp. If that was for your CPU, what are your idle and load temps on your GPU?
Is your CPU and/or GPU overclocked?
What is the make and model of your PSU?
When you say you've already installed all the new drivers, do you mean from a support disk or that you've gone to the support webpages for your components and loaded the latest drivers?
What make and model of motherboard do you have? Which BIOS version is installed?
A remote diagnosis relies completely on the information that you post here - the better the info, the better the odds of getting a good diagnosis and solution. There are many reasons why you're GPU could be crashing, assuming that it is in fact your GPU causing the crash. Going down the list, some of the possible causes are driver conflicts, out-of-date BIOS, faulty mobo, faulty GPU, faulty PSU. The list goes on. As best as possible, you want to eliminate all the possible causes you can so you can concentrate on the probable causes.