Hard drive not installed?

First thing to try is unplugging the system, removing or disconnecting the battery and then removing and reconnecting the hard drive.

If that doesn't get the drive recognized, the drive has failed.

If you require further information, we'll need the full model number of the system (i.e., Inspiron 7352, XPS L522x, etc.).

If it says "error code 0141, no hard drive detected", it's likely a "communication" problem between the drive and the drive cable and not an outright failure of the hard drive. It's a fairly common problem with Dell, my desktop is having the same problem as we speak. With desktops, Dell (Kashyap, at Dell Technical Support) recommends "wiggle the drive connections" and try to reboot. I'm not sure if that would work with a laptop but my desktop's back working until my new drive arrives tomorrow.

Please try these common fixes. 

1)      Try to connect it with some other working PC/laptop.

2)      Check that all Connectors are properly cabled.

3)      Test the port on laptop with which you are connecting.

Also, I recommend you to immediately take backup of your valuable data. If you considering to recover your lost data, you can opt for any reliable and efficient disk recovery software.

Remove the hard drive and connect it again. If you still face the same trouble, please connect it with other computer to verify whether your hard disk have any issues. If it is your hard disk's fault, replace the  hard drive. Otherwise check the connector, etc.