While trying to validate the installation of tensorflow-gpu, I get an ImportError when trying to execute \"import tensorflow as tf\". I am using a Quadro K620 on Windows 7.
I still got this error after installing cuDNN 5.1 (yes, I had PATH set correctly). I had better luck installing tensorflow_gpu from this site. This requires cuDNN 6.0, not 5.1. Unfortunately they currently only have Tensorflow 1.1 for GPU systems.