After my friends kept saying how awesome OSX 10.8 Mountain Lion was, I finally couldn't resist the temptation, and prepared to give it a try. So I grab the files, extracted the dmg, and then follow the instruction by use Disk Utility to restore the dmg to an existing Lion partition.
Problem comes, I kept getting verification error. It turns out that that's ok. All I need to do is first enable to partition, and then repair the partition. After that, I got the partition up and running.
Here's the next problem. I found that for some quick reason, the Capacity of the drive is 424Gb, but the actually usable size is just 8Gb! Later, I solved the problem by using Apple Disk Utility. First I slightly shrinked the partition, that forced the partition to recalculate, and finally reclaimed all the capacity of the partition. Then I enlarged the partition to the original size. And now I got the full partition capacity. Along the process, though, I need to do disk repair on the partition a few times. But eventually it all worked out.
Having enough disk space is so important. Because when I am out of disk space, crazy thing happens. For instance, I got error message saying that I had no privilege when I tried to change to start up disk, all because there's no space left on my hard disk.
I still haven't found Mountain Lion particularly awesome. Maybe I just need some more time to get used to it. But at least I enough the Chinese Handwriting feature.