large file uses massive memory - crashes

I have a large excel file that is 169Meg. I have used larger files before but this one is a problem. When opening, it instantly uses 2000-3000Meg of RAM.
I cant do anything in this file, when I copy or try to save it closes down. Can anyone help me here, and why would such a file use so much RAM (which obviously seems to be the problem)
thanks

Try saving it as a binary file. This seems to help when I deal with larger files. And if auto-calc is on turn it off.