Trying to use Bootrec.exe.. but some problems.

Well. I boot into my win 7 cd. Press repair. click on cmd prompt. Type in bootrec.exe. All of thew things show up, but when I try to enter a command it says "**** is not recognized as an internal or external command, operatable program or batch file." At first I thought it was because I wasnt running as an admin.. but then I look and I am running as admin.... after that I'm like DOH! its because of my system variables.. But I cant access my computer.. so I cant access system variables... Is there any way to change system variables in cmd? If there is tell me how to get there, and what to set the variable as.

Thanks you.