help me please

[Donn]

> hi,im totally new in linux.
>
Hello, welcome.
> i installed kubuntu a week 
> ago, but i met a trouble: i cannot turn off my PC. i
> click log out, then click turn off, soon the monitor
> turns black and displays several lines seems like it
> informs what the system do at that time.the last line
> write will now halt, but my PC never turn off. 
>
That sounds like a horribly common bug:
https://bugs.launchpad.net/ubuntu/+source/linux-source-2.6.17/+bug/43961

I don't really know what to suggest. Try this:
1. Open a konsole (Alt + F2, konsole, enter)
2. Try to shutdown the machine by typing:
sudo shutdown -h now
3. Observe the messages it displays on the konsole - if you can write them 
down, they might help fix the problem.

> when i 
> press power button, still it cant turn off, 
>
Try holding the power button down for over 6 seconds.

hth
/d