After I installed KDE4 two days after that my desktop just froze, so pulled the plug on my laptop and restarted it. It took a long time for the splash screen to load ,then it went,( Ithink to the openSUSE terminal) and it ask " Want me to fall back to /dev/disk/by- id/ata -HTS726060M9AT00_MRH400M461DL3A- part2? (Y/n)"

it couldn't find part1 of that, so i put Y(yes)

and then It was waiting the device ---part2 ............ not found -- exiting to /bin/sh

I have no idea what to do, can someone please help me.

Your openSUSE installation appears to have been damaged. The best thing to do at this time would probably be using a LiveCD to backup any data then reinstall.