The trick is to install Windows first, leave some space on your drive for Linux, and then install Linux. It's best if you install on a single drive (ie non-RAID) unless you know your RAID is supported in Linux.
I'd suggest Linux Mint (based on Ubuntu) or Ubuntu, although there are lots of other good distros out there now. Mint comes with a little more goodies by default and has some other niceties over a stock Ubuntu IMHO.
I think both Mint and Ubuntu's installers will automatically pick up your Windows install when you're installing Linux and create a boot menu entry to allow you to select which to boot.
Good luck!
