1. Although viruses do exist they are few in number in comparison to proprietary platforms (including MACS)
Why GNU/Linux Viruses are fairly uncommon
http://www.gnu.org/fun/jokes/evilmalware.html
2. Although there is WINE (windows compatability layer) which will run some games in general gaming is not the strongest in Linux so for the heavy gamer I would usually recommend a Dual Boot with XP which is more than capable of fulfilling the task
How to dual boot Windows XP and Linux (in this case as an example Ubuntu 8.04)
http://apcmag.com/how_to_dual_boot_windows_xp_and_linux_xp_installed_first.htm
3. Here are some options for installing or trying out Linux
Option One (Full installation)
I thoroughly recommend Linux Mint 9 Main Edition which is built upon Ubuntu 10.04 Its easy to install and easy to use plus it comes with much of the software you are likely to need preinstalled
Linux Mint 9 Download
http://www.linuxmint.com/edition.php?id=52
The Perfect Desktop - Linux Mint 9 (Isadora)
http://www.howtoforge.com/the-perfect-desktop-linux-mint-9-isadora
Linux Mint 9 User Guide Download pdf.
http://www.linuxmint.com/rel_isadora.php
You download the ISO. image of Linux Mint 9 then you need to create a Bootable LiveCD for installation
Linux Mint 9 can also be run direct from the LiveCD from Booting up without touching your Hard Drive
Also worth considering :
Fedora Remix (Fedora with elements of Linux Mint)
http://fcoremix.wordpress.com/2010/05/25/lucky-13/
http://iso.linux.hr/community-fedora-remix/
http://docs.fedoraproject.org/en-US/Fedora/13/html/User_Guide/
Again Fedora Remix can be run direct from the LiveDVD without touching your Hard Drive
Option Two (Install Linux inside Windows)
Installing Ubuntu as a dual-boot with Windows without partitioning
http://www.psychocats.net/ubuntu/wubi
You keep Windows as it is, Wubi only adds an extra option to boot into Ubuntu. Wubi does not require you to modify the partitions of your PC, or to use a different bootloader, and does not install special drivers. It works just like any other application.
Wubi keeps most of the files in one folder, and if you do not like it, you can simply uninstall it as any other application.
Boot in to windows insert the Ubuntu 10.04 LiveCD and you will offered the option of installing inside windows which is where the Wubi installer comes in, you will be asked how many gigabytes you wish to allocate to Ubuntu (I recommend 8gb) then you set a password for your installation then click install and thats it.
Once Ubuntu is fully installed upon starting your PC you will be given a choice of which operating system you want to use Windows or Ubuntu
Ubuntu 10.04 Download
http://www.ubuntu.com/desktop/get-ubuntu/download
Ubuntu 10.04 (Lucid Lynx) User Guide
http://ubuntuguide.org/wiki/Ubuntu:Lucid
Linux Mint 9 which is built upon Ubuntu 10.04 has a similar feature called mint4win and the directions given above for Wubi can be followed
As with Linux Mint 9 and Fedora Remix, Ubuntu 10.04 can also be run straight from the LiveCD without touching your Hard drive
Option Three (LiveCD)
Here the possibilities are endless as you can try out as many different Linux distros. as you like until you find the one thats right for you DISTROWATCH.COM gives full listings (second lists the major distributions)
http://distrowatch.com/
Major Linux Distributions
http://distrowatch.com/dwres.php?resource=major
LUg.