160gig only has 130???

My 160gig Maxtor SATA hard drive shows up in the bios as 163 gig but in windows it only shows it as havin 131 gigs in total... i'm aware that normally you lose a few gigs but... 30?! thats just a rip off!!! is this normal???

Awesome thanks!!! Haha thought i got ripped off was bout 2 start yellin at someone.