What is the easiest Linux OS to install and use, on a Y400 Lenovo Laptop with win 7?

Ubuntu: http://www.ubuntu.com/desktop

download the iso there and burn to a disk and boot from it, you can choose to install side by side.

to update the OS open terminal ctr+alt+T and type: sudo apt-get update and sudo apt-get upgrade

install compiz settings manager from software center and selecy wobbly windows for a nice effect.

linux (ubuntu) is like impossibe to get a virus on.

note you can install virtualbox and create a virtual drive to install it on but enable it in your host bios

I have been usung Linux for the passed 12 years. I download and test out every new releases, I would NOT recommend Ubuntu to anyone, there are better releases Here are some of the Linux distributions I would recommend you take a look at these
http://linuxmint.com/...xmint.com/
http://zorin-os.com/
http://kubuntu.org/
http://lxle.net/