<A target="_blank" href="http://www.pcworld.com/article/174710/microsoft_says_windows_7_install_workaround_is_legal.html?tk=rss_news">Installing Win7 to a clean hard drive is legal, according to Microsoft</A>, under some conditions. Basically, if your PC came with OEM version of Windows, even if you've lost the disks, you can install Win7 legally.