Photoshop cs4 Texture tools: dds filetype unrecognized

Hello. I am trying to open dds filetypes in adobe photoshop cs4. I run Windows 7 64-bit, so my adobe photoshop cs4 is also 64-bit. I tried installing NVIDIA texture tools for adobe photoshop (windows 64-bit), and the installation seemed to go well. I restarted my computer and then tried to open the dds file, but I got the following error message: “Could not complete your request because it is not the right kind of document”. When I check my Adobe plugins\file formats folder, the dds (.8bi) plugin is in there. So what have I missed?