Hey there. I've had a laptop (Toshiba Satellite A505-s6035) for the past 3 years. It's a pretty decent laptop and, even now, can run most games on medium-to-high settings well. The only problem is that it used to be prone to overheating. About a year and a half ago, it began to overheat during the more strenuous times, and eventually was overheating over incredibly trivial things (like photoshop). About a year ago, I replaced the fan (which was grinding) and applied Arctic Silver Thermal Paste to the CPU, and, lo and behold, it stopped overheating. I also bought a cooling pad and have been using it since. I have not had it overheat once since then, not even during incredibly cpu-strained gaming sessions.
About a week ago, however, this changed. A game I could play easily the day before suddenly shut down my computer about 2 or 3 minutes in. I tried other games, tried cleaning the fan, etc. Still happened. I am pretty sure ths is another thermal issue, but I am wondering why this is so sudden. I want to be sure before I open it up again. Is there anythign else that could cause my computer to immediately shut down within 3 minutes of opening a game?
Screwed-up software and/or viruses can have an affect on performance and stability.
Unless it is the software it has to be a thermal problem. Make sure your graphics cooling is good. cpu is not the only thing that needs good cooling. Graphics needs good cooling probably more so, especially when it comes to gaming.
Also maybe after a long time of use and strain some component(s) may have weakened and are starting to malfunction/die or even heat up more. Something like graphics, chipset, cpu, or motherboard. Other than that and possible software hiccups I don't see any other reasons for your shutdown issues...
An old POS dell I had would have a similar problem amongst many others so the first thing I would do is go into the car/home's air conditioning and put the computer air intake right up to it to make sure it stayed cool before I opened it. If it was getting to hot the aluminum fins were usually just full of dust.