when we are connected to computer it will be loading, but it will not be open

Hi there Arun Christo,

You will have to provide more information on the issue you are facing. As you have tagged this thread with 'external hard drive', I assume you are talking about an external hard drive that can't be detected by your system.
I would advise you to start with something simple as just changing the USB cable as well as the USB port. You can connect it to another computer as well. If the issue persists, you will have to go to Disk Management and see whether it has healthy partitions and file system. If not, you will have to use some data/partition recovery software in order to retrieve the data.
If the drive is not recognized by Disk Management at all, then I guess you will need to use the services of a data recovery company.

Hope this will help,
D_Know_WD