On windows xp ,we can get the hotfix infos form HKEY_LOCAL_MACHINE,(“SOFTWARE\\Microsoft\\Windows NT\\CurrentVersion\\HotFix”),but on windows 7 there is no that key. however we can get the hotfix  infos from here”HKEY_LOCAL_MACHINE\SOFTWARE\Microsoft\Windows\CurrentVersion\Component Based Servicing\Packages\”.Click here to down load the source code(not well written).lol