You have a few options here, but I will tell you the most effective way to fix the issue is going to require you to disassemble the laptop.
First, you need to establish how bad the laptop is actually overheating and what is causing it. Obviously it is heating up pretty well if it is powering off, but does this happen when the laptop is sitting idle or when you start putting stress on it (for example running multiple programs). Now one way to get a clear note of this is to install a temperature monitoring program. This will allow you to see approximately how hot your laptop is running and when. For this, I recommend a program called
"SpeedFan".
What you want to do is start the laptop, close all your programs that are running, download that and install it. Now with your computer sitting idle (no programs except SpeedFan), take a note of what your temperatures are showing. It is normal for a laptop to run anywhere between 100F - 135F sitting idle. Next you want to start opening some programs and seeing how the stress is affecting the laptop. If your laptop is going anywhere near 160F+, you have some issues.
Now like I said before, there are 2 ways to go about fixing this. Before you do anything though, you want to make sure your laptop has sufficient air ventilation. Make sure it is not crammed in between things or stuck in a tight spot. Any of this will cause heat issues. Now for your 2 options, like I said I recommend #2 first, but this requires some dis assembly. If option #1 does not work, and you are not comfortable with option #2, take it to a repair shop. It's not worth risking your system.
- This is the easier way out, but may only affect your temperatures 2-8 degree's. There is an item known as a laptop cooler, it basically is a plate you put under your laptop that comes equipped with fans. You plug it into your USB to power the fans and it helps circulate the air under the laptop. The pro's to this is it will lower your temperature a bit. The cons are that it may not lower it much, and it is an extra thing to carry around with your laptop. Now they normally run anywhere from $15-$50 depending on what you get. If you are interested in this method, I would recommend the online computer dealer "Tiger Direct"
Here are some pictures for you to better see it
- The more effective way to tackle this problem is to open up your laptop and get all the dust out of it, clear out all the fans, and clear out the heat sink. Dust is a leading cause of overheating in computers and can have a dramatic effect on the overall temperature. By doing just this I have had laptops internal temperatures drop more then 20F. Now taking apart the laptop can be tricky. For this I would advise finding a "Service Guide" for your particular model. A service guide is the manual technicians use, it breaks down how to disassemble your laptop piece by piece. You can usually find these by going to Google and searching "Toshiba Satellite xxxxx Service Guide" (where the x's are your model #).
Once you have your laptop apart you can blow out the fans with a can of compressed air. You can do the same with the heatsink (it is a copper piece on top of your CPU). DO NOT use an air compressor to do this, it can generate static electricity and hurt your system.
Sorry for the length of the post, but this should really help you!