You can't purchase or obtain the software anymore because it's not available for purchase. Version 6 was deprecated and replaced with the Windows 7 version, but it seems that the application is now used internally at PcWorld. There was the possibility to buy version 6, but it was removed soon afterwards. You can use another tool like PCMark 8 from the FutureMark. Access the website and scroll down until you see a trial section with the download link.