(1)download wubi;
(2)run wubi, it will begin to download a ubuntu release suitable to the hardware of the system.;
(3)because ubuntu release's size is big, it is not easy to download successfully by wubi itself;
my way is: after wubi ran, stop wubi's installation process once it has started downloadding. Go to the ubuntu's setup directory and find the actual release it downloaded. Use downloading assistant tools to download the ubuntu release, e.g. Flashget. Put it into a same directory with wubi, so that wubi would use the local version of the ubuntu release.;
(4)make sure setup the English version not Chinese version. I found in Chinese version, many new packages cannot be added using "sudo aptget install".