There are SO many different distros.
Go to http://www.distrowatch.com
, browse the different distros, read up on them, and find one you think will run smoothly on your system. There's tons of documentation on how to install it, configure, and run windows programs all over the net.
The most user-friendly distro out there now is Ubuntu (http://www.ubuntu.com
Fully user customizable and such, you can even run Virtual PC from Ubuntu, provided you have the right lisences.