Ok, I just installed Ubuntu 13.04 (Raring Ringtail) successfully -- by booting it with my USB stick with the help of "Universal USB Installer" software. I had also downloaded the ISO for older Ubuntu 12.04 LTS also, which has support for 5 years, where as 13.04 is only has developer support for only 5 months -- but has the newest features.
So I wan'ted to have Ubuntu again, so I downloaded the 13.04 version, which is not a fully tested version as far as i know -- though claimed to have all the latest features. I downloaded the ISO and loaded it with demon tools. But when i tried it to install via the virtual drive, I saw that the installation lacks the option to Install Ubuntu from within windows -- damn!
So.. I decided to burn the Ubuntu ISO to a disk and boot the computer with it. Because my burner is not working properly (I need ISO buster to open files I burn with my burner), I went to a net cafe to get it to a disc. And.. gosh, the lady in there did not knew how to burned an ISO image, so I had to assist her. So, I was able to get Ubuntu on disc. But when I got home and tried to boot from disc, I wouldn't work! (yes, I've set the boot option to DVD drive). So then I've concluded that something is wrong with my DVD drive -- damn again!
I don't know what to do now. Probably it will download the 12.04 LTS (fully tested verson) and install that.