The "Always On USB" feature that comes equipped on most IBM/Lenovo ThinkPads allows you to charge your MP3 player, phone and sundry gadgets even when your laptop is turned off. While this feature is turned off in most default factory settings, you can turn it on via the ThinkPad T400's "Power Manager."
Click the "Start" button (or "Windows" logo in Vista), then click "Control Panel."
Click on "Classic View" if not already selected, then double-click "Power Options."
Click "Power Manager" on the left to access your ThinkPad battery's properties, then click on the "Global Power Settings" tab.
Click the box next to "Enable Always On USB," then hit "OK." You will now be able to charge devices through the ThinkPad's USB port even when it's turned off.
If you still can't enable "Always On USB," visit the ThinkPad T400's official support site to download and install the BIOS update and restart the process.