Thanks for the help, I really appreciate it. But I finally reinstall Leopard on my iBook yesterday, since I can't fix it anyway. Tried to boot using target mode with my friend's Macbook, it worked and nothing seems to be a problem, but it just won't work when I boot normally. Then I decided to just reinstall my Leopard, and stick with 10.5.1 until at least I got new battery for my iBook. 😀
Thanks anyway!