Unavailability of 8 gigs out of 40 gigs

A while back I started the install process of Linux 8.0 with no problems. During the install process there was window that came up saying something to the effect “If wish to stop and not have Linux installed on your hard drive simply hit the reset button or ctl-alt-del. Well I hit the reset button to what would happen. I then repeated the process again and let the install process run in its entirety. However, I noticed that I was unable to utilize 8 gigs from my 40 hard drive. Is there a way I can recover this 8 gigs? Every thing is working very well so far. I appreciated any help.

Markus