Downloads:
32-Bit (3 or less GB RAM)
64-bit (4+ GB RAM)
Now, on YouTube, there's an amazing tutorial that a guy put up on how to install Windows 7 after you've completed downloading the ISO. However, his tutorial is for partitioning the HDD while using Vista, not XP. However, Here's a link to that - Click Here for YouTube Tutorial (LOL @ My comment.)
I finished installing this morning. I formatted my entire Hard Drive and installed Windows 7 as the Main (and only) Operating System on my computer. Here's a screenshot of my desktop:
(Click to Enlarge)

Good luck!