Boot

[Esbon]

 what should I do?

[WAWood · Accepted solution]

@Esbon 

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 hard drive: http://support.hp.com/us-en/document/c00439024

If not, to check the drive 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.

[Esbon]

I followed your advice and the disk was okay. Apparently it's a virus that erased everything. I am now wondering whether it's possible to recover some key data that i had stored in the hard disk

[WAWood]

@Esbon 

I have done data recovery a LOT and can tell you that Using Linux utilities to recover data from Windows file systems is asking for trouble.  You do much better using Windows data recovery tools.

All you will be able to recover at best from the drive is personal data. You will not be able to recover settings, website information (including user accounts and passwords) or applications.

Your best bet for recovering data now is to do the following:
1) Remove the disk drive from the old PC. If this is a SATA hard drive or a SATA SSD, this is a simple thing to do. If this is an m.2 SSD, that could be either screwed to the motherboard or soldered to the motherboard. If the second, you would need to have a techician remove it for you, or you risk seriously damaging the PC doing it yourself.
2) If you have a desktop PC with a spare hard drive connector, then connect the old drive to that. If the old drive is a SATA drive, connect both the power cable and the data cable. (This adapter is illustrated below) If the old drive is an m.2 SSD, you will need a USB-to-mSATA cable.

3) Try to retrieve the files and folders you want to save from the old drive and copy them to the new PC.

If this does not work, then you need to do the following:
1) Download and install this utility on a working PC http://www.majorgeeks.com/news/story/recover_data_in_3_steps_with_minitool_power_data_recovery_free_...
2) Run the data recovery utility to see what can be retrieved from the old drive.

If that tool does not find what you need, an alternative is Recuva http://www.piriform.com/recuva

And, if that does not work well, the best tool out there is this one, but only the demo version is free https://www.runtime.org/data-recovery-software.htm