Install Ubuntu

The iso file should be downloaded first. Then it is important to do a md5 check. In Windows, winMD5Sum is needed to do the check, which can be downloaded from
http://www.nullriver.com/index/products/winmd5sum
I first planned to install from hard disk.
Since I have already had a grub installed. Here is the steps after enter grub command line:

grub> kernel (hd0,4)/vmlinuz root=/dev/ram ramdisk_size=32000 devfs=mount,dall

grub> initrd (hd0,4)/initrd.gz

grub> boot

See also:
http://my.opera.com/bloodmelon/blog/show.dml/284393
For more info about initrd and ramdisk, see
http://firenet.ik8.com/doc/rd.html
Ubuntu is strange; it did not let me to select iso file manually, instead, it scanned to hard disk automatically. However, it was not capable enough to find that image. So it prompted me to insert CD over and over again. I went insane.
So I burnt the CD. Start from the CD, I first chose to manually partition the disk, but later I found that I didn't know how to. So I exit and deleted the partition of Fedora using PQ Magic. Restart the installation again, and this time I found there was an option create partition on the largest continuous free space, so I chose it.