I have never gotten a virus and don't understand how people get tons and how security companies make so much.

In the first place, the sort of people who are habitually catching viruses due to lack of basic care, are unlikely to be the sort of people who will choose to run a linux OS.

Secondly it's not an either/or situation at this point. XP is supported until at least 2014...... so if you already have it, there's no great impetus to abandon Windows in favour of an alternative.

Thirdly and again related to the either/or thing - if you are the sort of person that has a deeper interest in maintaining a clean install ...... with increased computing power and the heightened profile/accessibility of virtual machine technology - it's becoming ever more simple to run one or more linux distro's in a Windows host - it's not necessary to dual boot or make a hard choice anymore. Alternatively for those who prefer it, run a Windows machine in a Linux distro.... hey, run XP & Vista and Linux distros on the one machine if you have the resources to share .....

So Vista is just another option - the difference nowadays you don't just decide if you want to run it anymore at the cost of other choices - you get to decide where in a hierarchy you want to run it.