Portal wont work??!!??

I just got portal today, and im trying to install it but it doesnt work.

I put the disc in the CD-RW drive like usual but the drive says i dont have anything in it when i got to the My Computer screen! I even refresh it but it says theres nothing in there!

:cry: Please, i need help!

could provide a link to Steam website cause i dont know it unless its steam.comPrince2shadows

how do you do that because im on steam and im on the portal page but theres no button that says "download this game with activision cd-key!"

:cry: I start up the game but when i get to the loading screen for the menu it exits portal after a few seconds!

it says i dont meet minimum requierments! DAMN YOU DELL!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!