okay so this is what i did so far...
downloaded ubuntu 12.04 LTS from ubunutu website.
downloaded UNetbootin from http://unetbootin.sourceforge.net/
tried running UNetbootin as administrator too but still won't boot.
my laptop is HP pavilion G6 core i5 3rd gen. OS is windows 7 32-bit.
i don't know if this is anyhow related to this issue. i tried installing ubuntu(old version that i had written to a CD 2 years back). i booted successfully from CD but the installation was stuck in ubuntu loading screen. so i had to use the power button in my laptop to turnoff the machine and start again. didn't try that again and since the CD didn't work i decided to download a fresh copy(ubuntu 12.04 LTS) from website. so... now i am trying to install from usb because i am too lazy to go out and buy some blank DVDs :|
note: i have never installed or tried ubuntu before. so i am not sure what else i should do in this type of situation.