|That or it could be clogged up with crud, like dust a debris if you happen to live in a such an area. Overheating will do amazingly bad things to a computer. The other common cause of overheating is aside from the fan there are large heat sink plates that have to make physical contact with the item they are trying to wick heat away from. If they have become dislodged due to rough handling that can cause problems.
In terms of eating programs that could be due to a hard drive failure, do a scan for bad sectors or it could be due to heat which will shorten the lifespan of the hard drive by a remarkable amount.
All signs point to heat either a dead fan as dsupersad1 said or in some less than friendly parts of the world ingestion of crap into the fan intake.
1. Turn on the computer and look and listen for all fans to make sure they are turning. It should be obvious where they are
2. Turn off the computer unplug it and remove the battery
3. Open the case provided there is not a warranty void if removed sticker
4. Using either a can of compressed air (Do not use shop air it is much too powerful and will damage your computer) clean away any dust and gunk build up.
5. If you do not have canned air, a soft paint brush can work but BE GENTAL (don't say I did not warn you).
6. Visually inspect to make sure that all heat sinks and heat plates are in place
7. Check and make sure all connectors are properly seated
8. Reassemble and do not over torque the screws. You are only holding together two peaces of plastic not a cylinder head
If all else fails take it in.