Mio offers a Map Update DVD for its C310x model. You can order the disc at mapupdate.mio-tech.com for $69.95 (plus $9.95 for shipping).
When you receive the update DVD, turn on the device and connect it to your computer via USB. Insert the DVD.
On the main menu, select Update Firmware. If a message appears stating that the firmware on the Mio is the latest version, you can
immediately skip to Step 5. If not, it should take approximately 40 seconds to update the firmware.
When the firmware finishes updating, click OK when the Update Complete message appears. Disconnect the USB cable.
Re-initialize the Mio by sliding the power switch off, and then turning it back on. Complete the language and time settings.
Connect the Mio to your notebook via USB and click Update Maps.
The map selection screen will appear. Click Load Map.
The Map Updating Activation window will appear. Click the link to access the Web site to get the Activation Code.
Return to the Map Updating Activation window and enter the DVD’s serial number (found on the back of the DVD’s packaging), as well as the Activation Code. Click Transmit to Device.