It's a testament to the general uselessness of iTunes on Windows that so many useful apps have popped up that address its shortcomings. WindSolutions has the CopyTrans suite of apps, and the latest addition to this suite is CopyTrans TuneSwift (free until March 15; price thereafter to be determined). This app allows you to back up, restore, and transfer entire iTunes media libraries.
TuneSwift is as straightforward as can be. If you've got iTunes open when TuneSwift launches, it'll ask you to close it. Then, click a button for backing up, restoring, or transferring iTunes libraries. Make sure you have plenty of space for the backup and, as with any backup, place it in a different folder (and preferably a different drive) from the original. Transferring an iTunes library with TuneSwift moves and deletes the library, and TuneSwift's options include transferring to an external drive, another folder (such as a network folder) or a new computer. Transferring to a new PC is so similar to transferring to an external drive (as both require an external drive), that these options could have been combined into one button. Also, you can transfer libraries between a PC and a Mac, which is a welcome feature.
Restoring a backup with TuneSwift completely wipes and replaces your iTunes library with the backup, with no "Do you want to do this?" confirmation, so either make sure this is what you want, or restore the backup to a place other than the default iTunes Media folder.
One reassuring feature is that TuneSwift runs a simulation every time it backs up or restores, before doing anything, to make sure it's going to work right and that there are no errors. The vendor claims that if the simulation fails, the backup or restore won't proceed; however, it worked on my Windows 7 tester every time, so I didn't get to see the warning message.
As with other CopyTrans software, WindSolutions prefers you download their Suite front-end / downloader app first, and then choose which CopyTrans apps to install from within that. However, you can also download the Tuneswift ZIP file here, which houses the EXE and RIS files you'll need to install Tuneswift alone.
Like many CopyTrans Suite apps, TuneSwift is another essential piece to get iTunes where you want it to be.
Note: TuneSwift is shareware, and its future price is unclear; however, it is free through March 15, 2011. The full version is activated by copying and pasting an activation code from the vendor. The secret link to the code can be found through the TuneSwift app itself; or PCWorld readers may use the code TUNESWIFT-PC-WORLD through March 15.