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Plug in the phone to your PC with the USB cable and then enable storage mode. If the screen doesn't pop up right away when you plug in the phone, pull down the notification bar and tap on the USB connected notification. Once storage is enabled, your phone will show up on your PC as a removable drive. Copy your pictures (in the DCIM folder) from there to your PC.
Alternatively, HTC provided sync software which you must download and install from their website. For specific instructions with that you can ask the members in HTC Sensation - Android Forums