If the hard drive can't be regonized or too old to use, then the d3dx9_27 dll strong error may popup. By the way, good using habit and regular maintenance will extend its life span.Third -- Unreasonable startup or shutdown operation.
Have you ever forced a shutdown operation to your personal computer with programs running? It's quite bad thing to do, violent and harmful to computer, and yes, it will lead to d3dx9_27 dll strong error.Fourth - Incomplete or defective third party applications.
Have you installed any suspicious softwares and whether the errors stared to popups after installation? If so, you will need to uninstall those programs first.