Laptop cannot start

I own a samsung r418 laptop with a broken dvd drive. I wanted to install windows 7 and so i virtually mounted the setup on my windows and begin the setup and this is where it get screwed up..while the setup runs it restarts the system a couple of times automatically which is normal..but unfourtunately my setup was unterrupted by an unexpected restart which led to the incomplete installation...and it asks to restart the system so that itcan continue the setup but when i restart it it comes back to the same dialogue box saying to restart to continue and again the same thing after another restart..since my dvd is broken i tried to boot the system using a portable hard drive containg the windows 7 setup...but all i can see is a black screen with a blinking hyphen.and the stable light on my portable hard drive indicated tht the system is not even reading the hard drive..(if it's being read the light blinks.)i've tried all option i cud find..running in safe mode, repair system,run last good know config.but nothingworks...it all comes back to the windows installation dialogue box asking to restart...friends please help me out..i love my laptop it's my best friend nd i cnt spend a day without it.