I'm probably not the only who got stuck in this unfortunate and awkward setup: having a state-of-the-art mobile device (in this case Samsung Galaxy Nexus) while still on an antiquated desktop O/S, which is Windows XP. Who runs Windows XP on a brand new i5 2400 with 8 GB DDR3?? Guess that's story for another day. Anyway, one problem with the setup is the USB connection between the two. Android 4 (ICS) has adopted a new way of presenting itself to the PC: MTP. As such PC would view it as a media player, and in turn seem to manager it with Windows Media Player (WMP). Vanilla Windows XP has WMP 6, which came out at a time when the world knew no iPod. Under its ignorant management, copying most files from PC to an ICS device was impossible - you'd be greeted with an unpassable "file type not supported" message, even though you thought you were just dragging files from one Explorer folder to another. To solve this nuisance you'll need to upgrade your WMP. I got WMP 11 installed and all became well for me - now I can copy any files (with only an easily dismissible warning message). Thanks for the hint provided here, and hopefully another tortured soul between the past and the future would benefit from this tip.