Ok, this is the situation. I try to boot into my computer but suddenly it says no boot device so I went into my bios to check my hard drive. At there, in the sata list it shows that I only connected to my DVD reader but not my hard drive. So I changed the location of the sata cable on my mobo to different port. Then, the bios recognize my HDD. After that, I boot into my computer and it works. The next day when I want to open my computer again, the problem repeated and I did the same thing again. Now, everyday I have to boot into my bios, change the cable location to another port and use my computer. This is frustrating. Please anyone provide me with an explanation why it happens.