I got this off the Sony site (can't post a link as a generic one is being created):
1. Connect the player to the computer.
2. From the computer, select start - Control Panel - Performance and Maintenance - System. "System Properties" is displayed.
3. Select Hardware tab, and open Device manager.
4. Open Universal Serial Bus controllers, and select USB Mass Storage Device or WALKMAN NWZ-XXXXX.
5. Select Action - Update Driver ... from the menu bar. "Welcome to the Hardware Update Wizard" is displayed.
6. A dialog on Windows Update connection will be displayed. Select No, not this time., followed by Next.
7. Select Install from a list or specific location [Advanced], followed by Next for the hardware install method.
8. Select Don't search. I will choose the driver to install., followed by Next for the search and install option.
9. Check Show compatible hardware, and then select MTP Device* in the model list, followed by Next. The device driver is installed.
10. "Completing the Hardware Update Wizard" message is displayed, and confirm "MTP Device" message. Click Finish.
*MTP: Media Transfer Protocol