I have landed myself with this problem by attempting to initiate a "Clean Boot" to cure problems in getting the upgrade app for windows 10.
I have Windows7 Professional on my PC,
Unfortunately as I started the first part of changes in the config sys. I inadvertantly clicked on enter!! Result is I now cannot get windows 7 to load anything past the logo.
My problem now is how do I get back into the config sys to make the changes, as my PC at start up wont do anything but load drivers at the Safe mode page ( command prompt just doesn't come up) I'm at a loss as what to do next, I don't want to reload windows and lose everything.