You mean the amount of disk memory you are using? There are a couple of ways, but one way is to go to windows explorer, right click on your local disk (C drive) and look under properties.
My C drive has 203GB of 296 free.
So a Win7 64bit 2.4Gh 6GBDDR3 500GB Hard drive that has DDR3 SDRAM Intel Corei3 should do it?