I have an acer all on one and a few days ago it *** off all by itaelf and when it came back on it said reboot and aelct boot device or.reboot and insert boot.media. I figured the hard drive was bad so I.put a Jew one.on now when.I turn it on the acer screen comes up then it goes to the last known good configuration or safe mode or start windows normally screen. No matter what I select it starts to boot up.but right after the acer screen it goes eight back to the safe mode or last known config I need to get this computer going again. I took the hard drive to my other desktop and installed xp on it. It starts Ho fine ok my desktop but won't start up on this computer. Can I not go from 7 back down to xp.