Anything with Socket M is physically compatable, if you want to be sure then look at the acer website and see if there was some higher spec'ed models in the range and get the processor from the top of the range system at the time.
check the socket. You also need to make sure the bios for the laptop can handle whatever you put in it.
I'd also check to see if the processor is soldered into the socket too. there are a number of laptops that you can't remove the processor from as well.
my laptop is acer aspire 4720,my processor is intel core 2 duo 1.5ghz,667mhz,my ram is 1gb ddr2 and i use window 7 ultimate,i really want change my processor laptop,but how i must know what processor suitable for my laptop??i hope someone can help me...