Kernel Panic error when installing 12.04

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http://askubuntu.com – I'm getting this error kernel panic not syncing vfs unable to mount root fs on unknown block (2,0) while installing 12.04 LTS desktop version for the first time on my laptop which is running on Windows XP. I'm trying to boot the same from USB wherein I have already extracted the 12.04 LTS .iso image file with the help of Universal-USB-Installer- I'm completely new to the Linux environment thus have no idea as what exactly is going haywire. I did a bit of net surfing and found out that I'm missing initramfs for kernel. Can anybody suggest how to choose anther kernel from grub menu (HowTos)