Acer aspire harddrive not showing real amount of disk space.."vista of course"

hi i have a acer aspire with windows vista.just got it about 3 or 4 days ago.my harddrive is 320gb sata hard disk.but when i go to my com etc all i see is 82.2 gb free of 113 gb.now im sure there is a reason.but im oblivious to it.any chance i could get some light shed on this problem.and also if that means i have less space to use if its being used somewhere else.also another question is how do i get into my second harddrive when i hook it up.it wont let me cause i dont have "permission".i realllly dont want to have to redownload the patches for wow lol. and want to transfer everything from one harddrive to my new one.so also could use some help on that.hope to hear from you soon!:-)