I am currently using Windows 7.
I downloaded the ubuntu's iso file from the official site. I don't currently have a pendrive and my laptop doesn't have any CD/DVD drive either.
I found a tutorial to boot iso files from windows boot loader using "EasyBCD". I followed it and restarted and it showed me the option to run the ubuntu's image file.
Edited:
It runs now, the ubuntu logo loads and reaches the command line again with this
(initramfs) unable to find a live medium containing a live file system .
The process is stuck here and I'm a complete newbie to Linux/ubuntu. Please help me out.