Slow Calculation

What hardware has that PC, I mean, how much ram does it have; you aren't using a small file. Does the harddisk need cleaning and defrag ?

its a dual core with 2 gig ram. hard disk is kept very clean using ccleaner & defragler twice a week .. the odd thing is when i input a value/text in a blank cell and press enter it calculates slowly and if I press enter twice it calculates instantly ..