Aspire 5634LMi overheats and switches itself off

I know Nero hogs system resources but today after spending almost two hours on burning a dvd using Cyberlink Power Producer, the laptop became overheated and switched itself off What a waste of time. The files were more than 92% encoded and burning was about to start and all of a sudden it died on me. This is happening more frequently these days. Yesterday kids were watching a twenty minute movie (Shrek the Halls) and it died on us. I usually keep it on the arm of the sofa balanced in the middle in order to allow free air circulation underneath. Now it is working OK as if nothing happened. I am fed up of wasting time this way. The machine is only 8 months old. Maybe Core2Duo (T5600 1,8 ghz) runs too hot for a simple laptop fan. Maybe some program is hogging system resources causing the processor to over-work itself. Should I format the HDD as C drive has only 7 gb left out of 60 gb? I had shut all extra programs even the antivirus (F Secure) and was browsing Wikipedia while it was encoding the videos in background to burn the DVD when it switched off.

Should I contact Acer as the machine is still under warranty?
Should I format the HDD to eliminate any sneaky program hogging system resources?
Should I flog it off on eBay and buy an Macbook?

Please help!

 

Shifted a lot of data to partition 'D' from where it will eventually moved to the external HDD. It improved things but still far from perfect although I defragmented the 'C' drive and checked it for errors using Scandisk as well last night.

 

Sounds like the classic overheating problem.

Contact Acer and have it setup for repair. http://global.acer.com/about/webmaster.htm