Windows Boot problem

I have a computer with Windows installed

Some days ago, Windows stopped with a BSOD ( 0x0000007A ). I don't know the reason because I haven't added any new device or so for a long time, but this is not the most important now ...

The important thing is that when I restart the computer, now it doesn't found Windows and after some seconds shows something like: "Reboot and select proper boot device"

So, I restarted the computer again and press F12 showing these entries ( both were created by Windows installer when I first installed Windows ):

1) Windows Boot Manager ( PO: WDCxxxxxxxxx-xxxxxx )
2) PO: WDCxxxxxxxxx-xxxxxx

If I manually select 1), Windows starts correctly
The problem is that I must do that every time I restart the computer

So, looks like something got misconfigured at boot level

Any solution to fix this boot problem?

Thanks