I need elevation on windows vista helpppp?

So, im trying to flush my dns on Command prompt, im already logged in as the administrator but it says i need elevation, im confused im supposed to be able to right click on command prompt and run as admin. but there isnt an option for it, on my user accounts i AM logged in under administrator so i dont get it. I have tried going into the computer and finding another way to be administrator, some "master" account but i think i already AM the master account because it says im administrator...pleeeeease help me im computer illiterate and i have to fix this so i can play on battle.net without getting disconnected ^^