Laptops freeze for many reasons. Since you've eliminated the easy ones I'll take you through the hard ones. Freezing other than software is caused by a temperature failure of the RAM chips, the video chip, the video ram chips, slow or non moving fan, dirty heat sink or failing CPU. You can take out your RAM chips one at a time. If the problem goes away then thats the culprit. (Take out the RAM chips with the computer off). You can clean the heat sink yourself. Get a can of compressed air from an office supply store. Somewhere on the back of your machine there are exit vents. Turn the unit off and unplug it and remove the battery. Spray the can of air into the vent area. Now put the battery back in and plug the charger in. Turn on the unit and determine if there is air flow from the vent. If you can't feel it with your hand then holding a single ply kleenex in front of the opening may help. If there is no air flowing from this vent or very little air then the fan is/has failed. To replace the fan requires a strip down of the computer as well as all the other chips that I mentioned that could be bad. Take it to a reputable repair person or check my website www.micromendllc.com. Good Luck