Top left corner blinking cursor (underscore)after power on with black screen

[Vijay_216]

Suddenly my pc got restarted while I using the internet after restart it stuck on the blinking cursor (underscore) with black screen  , 

[WAWood]

@Vijay_216 

A blinking cursor on a black screen indicates major corruption of the internal drive -- to the degree that the boot loader can not even be found.  IF it was found and there were simply Windows issues, you would have seen a message like "No Operating System".

This issue is often due to a failing drive.

So, let's check that first, because if it is failing, it would need to be replaced and there is no point then in doing anything else until we confirm that.

If your PC is new enough to support UEFI, you can use these steps to test the HDD (Hard Disk Drive): http://support.hp.com/us-en/document/c00439024

If not, to check the HDD you have to follow these steps:
1) Press Esc key repeatedly, several times a second, while rebooting the laptop. Do NOT hold the key down, just press it over and over.
2) Eventually, you will see an HP Startup Menu
3) Press the Function key for testing the hard drive (usually F2) and let it run.

If the drive checks out OK, then report that and I can provide you options for reinstalling Windows on your PC.

Please note that if your model has an SSD instead of an HDD, these diagnostics might not work properly.