External Harddisk Disappear

Have you tried other cables? Can you hear the disc inside the harddrive start to spin up when you plug it in? Shot in the dark question, have you reformated your computers main hard drive anytime recently with a fresh OS?

It's likely that the drive's partition table is corrupt. If you have a boot environment disk you can go into the partition table and find the fault. You may also be able to perform an fdisk or fsck and this may recover the MBR (Windows? Sinc you mentioned "device manager") however unlikely. The repair function of Windows may also help, but also highly unlikely. You will most likely need the boot env and do it manually. Do you possibly have a copy of the partition table? The would be immensely helpful in your cause.

External HDDs can require more power than is available from some earlier USB ports. Most USB 1.1 & 2 ports give out 500mA, so either a special cable to take power from two ports (but data from one) is required, or an external power supply for the HDD.

All Apple products use 1000mA USB ports. Many others have one high-power port and the rest low-power, even in desktop devices front/back split is common. USB3 provides more power.

Dear All

I plugged my harddisk and hear beep sound. from my computer cannot see my harddisk but in the remove safely it show. any advise to recover all my file. (photo,video,document).

Regard

Moh'd

A single beep is usually normal.

Have you tried using the HDD on another computer to check whether the issue is with your computer or with the HDD?