my harddisk just suddenly can't detected, try many times but it seems didn't success. Anyone got any idea how to do it? i got many important data inside, pls help, thanks in advance.

Maybe a cable is loose. Check inside.

If your PC is properly configured and can't talk to the drive, then the drive has failed and should be replaced. But before you run out and buy a new drive, make sure the PC is properly set up. Check the power and signal cables to the drive, then enter the system's CMOS Setup and make sure the drive is listed. If the CMOS Setup can't detect the drive, it is probably defective. Next, reboot the system to DOS and run fdisk to check for partitions on the drive. If fdisk can't locate or access the physical drive, it's probably defective. If, however, the drive is detected under the CMOS Setup and reports partitions with fdisk, a logic problem on the drive (such as a corrupt master boot record) may be preventing the system from booting. Repartition and reformat the drive, then reinstall Windows and your applications.