By default, iTunes on Windows only supports multimedia keys when in focus. MmKeys.dll is a tiny (44K) addon which just needs to be dropped into your iTunes plugins folder to add support for most multimedia keyboards even when iTunes is running in the background.
I’ve been using it for the past couple of weeks and have found it really handy!
Ben Pope has created a registry file for Windows which fixes a few annoying features of newer Logitech keyboards. By remapping keyboard scancodes, it effectively inverts the effect of the “F-Lock” key so that the F1-F12 keys work as standard function keys when F-Lock is off. This means you don’t have to turn F-Lock on every time you boot your computer or restart Windows.
The registry patch also remaps some of the media keys to return the Windows standard keycodes, which for me has stopped the annoying behaviour of the “Play/Pause” key which will sometimes start playing my current Winamp track from the beginning instead of pausing it as expected.
There are two caveats, though – firstly, it will only work when connecting the keyboard via PS/2, not USB (I’ve never seen the point of wasting a USB port when there is a dedicated keyboard port anyway), and it will cause you to lose functionality of some of the special keys.
I’m beginning to think I’d be better off with a “cheap and cheerful” keyboard rather than any of Logitech’s or Microsoft’s current offerings – anything with a standard keyboard layout, no F-Lock key, and play/pause and volume control will do the job.