There is no catch about that. You don’t need powerful software to support 3 virtual XPs to run XP mode in Windows Virtual PC, or anything like that. When I heard this being possible on an old PC with no real prerequisites, and for free, I was amazed.
In short, there is a French guy who developed a piece of software to handle all these versions under one title: IETester. Here is the link to the home page:
And the download itself (version 0.4.1):
Give it a try, you will find no better. And it’s for free. I’m not affiliated with the website, I don’t get anything from the sales or ads. But this guy happened to save our company by introducing this software. We no longer need to keep development servers up and running, or buy expensive hardware to virtualize locally or stay with XP only because it supports IE6. We are just a small company and this is my personal thanks.