You may try any of the following, listed from most convenient to least:
1. Try a different USB port or a different data cable;
2. Upload your images to OneDrive over Wi-Fi then download them in your PC through the same OneDrive account - since the HTC HD7 is running Windows Phone 7, you may need to go to onedrive.live.com through your phone browser to upload your photos;
3. Transfer via Bluetooth;
4. Attach your images in an email sent to yourself - unfortunately this method will decrease the quality of your images.