Windows will always make the best effort, when you plug in a new device to your computer, to try to automatically download and install the recommended drivers from Windows Update. This is a good feature to make sure that your newly installed hardware works properly, but not always the installation will go as smooth as you would like to. Sometimes the drivers from Windows Update are not the latest drivers, the installation could cause file corruption, or there could be other problems for uncommon devices.
It would be preferable to install your own drivers downloaded from the manufacture website or from the CD that came with the device.
To disable Widows 7 from automatically installing drivers, do the following: