how to get rid of "insert system disk and press enter " error?

I am a software engineer and I have my own shop for repairing CPU and PC and daily I am handling this type of problem. So I will advice you that whenever you get "insert system disk and press enter” error, than you should be very careful. As many times it may be a pre warning for disk failure. Don’t worry as you just have to take the regular backup to get rid from this problem. It is better to invest in good backup software. And whenever you will get this error than the solution for this is only one and that is very simple to, you just have to replace the disk and then press any key and the problem is solved.