excel “out of memory” but I have memory.

Here is my specs.
1 Gigabyte DDR memory
2 page files each 1 gigabyte on different hard disk( this was different and I changed it and it didnt make a difference)

I open one spreadsheet thats 65+ megs.
I try to open another spreadsheet that is 30+ megs with a lot of it being calculations.

Everytime I do this I get “Out of Memory errors”

My computer still has 500+ megs available

Any ideas?