For the past month or so, I've been leisurely migrating to Windows 7, at my own pace. I'll show you how to finish up the process by migrating your Apple iTunes library and copying over your data.
Move Your iTunes Library
Copying over your iTunes library is a drag and drop procedure, though it may take some time.
Start by making sure you're running the latest version of iTunes in your original version of Windows (XP or Vista). Then boot to Windows 7 and install that same version of iTunes. Any mixing of old and new iTunes library files could lead to unpleasant results.
While still in Windows 7, exit iTunes, then click the Windows Explorer icon in your taskbar. (Wasn't it nice of Microsoft to finally make Windows Explorer readily accessible?)
Browse into the Computer section. Find your original Windows XP/Vista partition (on my system it was Drive D:, even though it appears as Drive C: when I boot to that partition), then navigate into the Users, Your Username, My Music, iTunes folder.
You should see various iTunes Library files and subfolders. Now, find the corresponding iTunes folder in your Windows 7 partition, but don't open it. Instead, select all the files and folders from within the original partition's iTunes folder, then drag them to the new partition's iTunes folder.
Depending on how much music, video, apps, and the like you have, the copy process could take anywhere from a few minutes to an hour or more.
Along the way, Windows will likely notify you of a few duplicate files. Make sure to select the Copy and Replace option, as you want to overwrite the newer (and mostly empty) iTunes files with the ones from your original installation.
Once Windows has finished copying everything, start iTunes. Everything should be exactly as it was in your older OS. One cool exception: When you mouse over the iTunes icon in the Windows 7 taskbar, you'll see Play/Pause and Skip controls you can use for music playback without needing to maximise the program.
Copy Important Data
It's time to start wrapping up the process, installing any programs that didn't get installed earlier, copying over data files, and setting up peripherals like printers. In other words, the time has come to start living under Windows 7's roof, returning to XP or Vista only when necessary. Before you turn off the lights and lock the door, however, make a list of the programs you still need to install and the data you need to copy. Allow me to help with the latter.
Here's a list of common data you'll want to make sure you don't leave behind:
Documents: Everything in your My Documents folder, and in any other folders you use to store Word files, spreadsheets, presentations, and the like.
Music: If you don't use iTunes, or you keep your MP3s in a folder other than My Music, make sure to copy them over.
Photos: Most folks store them in the My Pictures folder, so all you have to do is copy the contents to the eponymous folder in Windows 7. Same goes for...
Videos: Most folks store them in the My Videos folder, so copy the contents to that same folder in Windows 7.
Financial records: If you use Intuit Quicken or Microsoft Money, your best bet is probably to use either program's built-in backup option, saving the backup file(s) to an easy to find spot on your Windows 7 partition (the Documents folder, for example), then run the program in Windows 7 and restore the backup.
Email: If you use Gmail, Yahoo, or another web-based email service, you're golden. Just sign into your accounts as usual using your browser. However, things are a lot trickier if you hang your email hat in Mozilla Thunderbird or Microsoft Outlook, Outlook Express, or Windows Live Mail. Because I can't cover the migration steps for all those programs here, I advise you to do a little Google searching and find the instructions you need. They're out there.
As I've noted before, the beauty of this slow migration is that if you forget something, no problem: You can copy it over as needed.
At some point, perhaps after a month or so, you can make this move more permanent by shrinking the partition for the old OS and enlarging the one with Windows 7. I'll cover that at a later time.