Yes - you should have posted this in your original thread, or at least given a link to it -'cos now it's not clear what you want, or where you got to before.
The message means your hard drive cannot be correctly identified as a boot disk, so the OS cannot be started, for some reason or another.
If this message appears sometimes but not others, it could be :-
Your hard drive is a bit lazy starting (often a sign of more trouble to come)
Read errors are occuring, which sometimes are gotten over by rereading, but sometimes not.
There is another intermittent fault that interferes wih the drive reading process - RAM, motherboard, cables, etc.