|Sounds like a typical overheating problem. If you're familiar with Laptop disassembly it would be a good idea to open the case and blow out the accumilated dust and debris, using canned Compressed air. You can purchase this at your local Computer Store.|
Otherwise find a Computer Repair shop that will clean it out for you. Be aware that it's very easy to create more problems than you'll solve if you do not know how to do this properly.
If you're willing to try it yourself, here is a Disassembly Guide. Go through it first and read up on the steps involved before you grab your tools.
Disassembly is easy, getting it all back together and working is a different story.
There is nothing to learn from someone who already agrees with you.