@nilll two things come to mind. Either your System can no longer access your hard drive or the OS can no longer be identified due to a corrupt file system or corrupt HDD. Create a bootable USB drive with something like a LINUX LIVE software and boot your computer from that. See if you can access your computers hard drive from that. If so, you know that reinstalling the OS should in theory work. You cannot do that from the recovery partition of your HDD if it is not accessible but will need another way to obtain the OS.