I have an Acer Aspire 6530 laptop, unfortunately (and it's done this for a while) when multi-tasking, especially when playing YouTube videos or films, the Laptop throws a complete wobbly and turns it's self off, no warning at all....any ideas????
Sounds off hand like thermal shut down. I'll suggest looking for disassembly instructions on youtube and cleaning out the heatsink. Unfortunately, disassembly is the only way to clear the heatsink of dust bunnies once formed, compressed air does little to move them and they just come back quickly. In some cases, removal of the heatsink is required (then you would want to change thermal compound). I'll also suggest monitoring your temps with CoreTemp or SpeedFan and the use of a laptop cooler.