Everything above is very valid and True.
Linux is a free OS, for a given value of free.
It is a good OS, for a given value of good.
As with all IT applications, you have to consider if you are applying the correct tool for the task you are trying to achieve.
If you are familiar with Windows, you will find that Linux is significantly different, at the end of the day it is written by techies for techies. Microsoft do get a lot worng, but they also get a hell of a lot right, especially around useability and functionality for novices.
Of the many falvours of Linux availible, I think you could do a lot worse than Ubunto
http://www.ubuntu.com. Download the latest version (7.10 I believe) and run the Live CD, you simply boot from the CD and Ubuntu runs completely off the CD, without making any changes to your system. Ideal for finding your feet. The downside is, you cant save any settigns this way.
If you want to do that without messing about with multi booting or loosing windows XP, you need to download VMWare Server from
http://www.vmware.com it is free and allows you to run Virtual Machines - essentialy a new computer in an isolated environment within your windows session. You can even download preconfigured Virtual Appliances running Ubuntu from VMWare. The best thing is this powerful tool is Free!.
As an IT professional, I make extensive use of Windows, Unix and VMWare environments, I could ramble at great length on the pros and cons of them all here, but I wont. Feel free to PM me for more information though.
I would also add, on the issue of spyware and virii: We wouldnt play without protection, so why the hell do we surf without protection. You should always be packing AntiVirus and AntiSpyware at the very least. There is no excuse, especially with several good quality free products availible.....