Save ALL your important data, program installers (with license keys), bookmarks/favorites, network configs, etc. to an external hard drive. Do a fresh install of winders 7 (make sure the hardware is compatible). Then reconnect to your network, reinstall programs, and move data back.
Figure a weekend worth of time.
I recently did this for two PCs. Easy Transfer is good, but not perfect. I used a networked external hard drive for the Easy Transfer files, but found that a lot of data wasn’t included if the default storage locations (pictures not in “My Pictures” for example) didn’t have all the data you wanted to migrate. Pay particular attention to where that stuff is on the XP install, modify the default Easy Transfer settings to match, and also make a separate backup of anything critical just in case.
Make a list of programs you like and need (7-Zip, a PDF reader, etc) so you can re-install the W7 versions after the switch, and make sure you know if you are running 32 or 64 bit W7 so you can choose the right versions.
Be prepared to wait a long time for all the W7 updates to download and install. I think the earlier estimate of a weekend for the project is a good one.
Also, I went from two ten year old PC’s to new machines, and didn’t have to worry if my old hardware was up to W7 standards. If you plan on loading W7 on an older XP PC, you might double check the system requirements for W7.
Good luck.