Drivers will need to be installed to the computer so that the Garmin device can communicate with your computer correctly.
This only applies to Garmin GPS Units that specifically communicate using Garmin USB Mode. This does not apply to Garmin GPS Units that are Mass Storage devices such as the nuvi and zumo units because they use drivers that are built into Windows. To do this, you will need to download the drivers from the Garmin website and install them.
Starting at the USB Drivers Download page: http://www8.garmin.com/support/agree.jsp?id=591
If you have not plugged the device into the computer, do that now.
Win XP: When the hardware installation wizard opens:
For most issues relating to Device not responding, or something similar, it is more than likely due to Windows failing to automatically detect the correct drivers. To manually direct windows to the correct drivers, go through the following steps:
Notice under Garmin Devices the entry with the yellow exclamation to the left of it. It may not necessarily say USB Device. Other names may include Garmin USB GPS, or Unknown Device.1
Your drivers should now be installed successfully. Once the drivers are installed, you can continue to work with the device. Running the latest updates to the device are a good idea. Please see WebUpdater to install updates: http://www8.garmin.com/products/webupdater/howtoinstall.jsp
1 If there is no entry named Garmin Device or Garmin USB GPS, look for an entry anywhere down the list (normally towards the bottom) named Unknown Device.