I thoroughly recommend you take a look at Linux Mint 7 Main Edition which is built upon Ubuntu 9.04 Its easy to install and easy to use plus it comes with much of the software you are likely to need preinstalled
Linux Mint 7 Download
http://www.linuxmint.com/edition.php?id=38
Linux Mint 7 User Guide
http://www.scribd.com/doc/15884753/Linux-Mint-7-Gloria-User-Guide
The Perfect Desktop - Linux Mint 7 (Gloria)
http://www.howtoforge.com/the-perfect-desktop-linux-mint-7-gloria
You download the ISO. image of Linux Mint 7 then you need to create a Bootable LiveCD for installation
Linux Mint 7 can also be run direct from the LiveCD from Booting up without touching your Hard Drive
After trying out Linux Mint 7 you may think twice about Windows 7. If gaming is an issue then XP is the way to go on a Dual Boot with Linux
How to dual boot Windows XP and Linux (XP installed first)
http://apcmag.com/how_to_dual_boot_windows_xp_and_linux_xp_installed_first.htm
ALSO WORTH CONSIDERING FEDORA 11
Fedora 11 Download
http://fedoraproject.org/get-fedora
Fedora 11 User Guide
http://docs.fedoraproject.org/user-guide/f11/en-US/html/
The Perfect Desktop - Fedora 11 (GNOME)
http://www.howtoforge.com/the-perfect-desktop-fedora-11-gnome
CURRENT SESSION
Linux Mint 7 ext4 with Compiz 0.8.2
http://www.linuxmint.com/edition.php?id=38
http://wiki.compiz-fusion.org/
LUg.