If you get this error message during POST when you turn on your computer, I have a solution: “Scan Devices, Please wait… no any device exists!”
This happened with an Asus P7H55-M/CSM motherboard. It gives the error after scanning for about 30 seconds, then when going into computer it also slow. Two seperate issues here.
To address the scan devices error on startup, we need to go into the BIOS, under Advanced tab, click “onboard devices configuration”. Then click on “VT6415 IDE controller” you can set it to disabled. Save and reboot. Fixed!
The issue with the computer being slow after booting into Windows is the video driver as you would have probably suspected if it were not for this other error. Windows 7 installs the driver automatically, but it is not a good one. Use the drivers DVD that came with the motherboard and install the video driver from there. It will most likely prompt you that you are about to install an older driver than what is already installed or the best one is already installed. Ignore that and continue anyway. After installed, shut down and start the computer again and make sure it is working fast now. It should be fixed with that simple procedure. Good luck!