I was about to write that I didn't quite understand the USB options that are given to me when I click on my USB connection in the Notifications screen when I'm hooked up to my PC. When I switch to "charge only", my Windows Media player still sees what's on the Droid X (Android 2.1), and when I try to use Media Share on the Droid X, it still says "SD card busy". But now I'm in a real pickle, because I changed the setting to "charge only", unhooked the phone, and then reconnected to the PC. Now the USB connection is no longer showing up in the Notifications area, despite multiple reconnections, and now WMP doesn't see what's on my phone, and now I can't figure out how to switch back to one of the other options. FOLLOW-UP: After restarting the phone and the PC the USB connection is working again, so that was just a separate glitch. Getting back to the main point: even when I'm in Charge Only mode, the PC can see the phone's contents in File Manager. Windows Media Player doesn't recognize the phone as DROID as it does when I'm in Windows Media Sync mode, but instead calls it E: and still lists its contents. Bottom line: what is the significance of the four modes: PC Mode, Windows Media Sync, USB Mass Storage, and Charge Only?