This is a Dell Vostro 3550 laptop that came with Windows 7. Today, Windows 10 installed automatically, without user intervention. The problem is that Windows 10 can't finish the boot process . After the first few seconds of booting, it stays on a black screen forever. Nothing I tried changes that. I would like to try to manually roll back to 7, by connecting the disk to another PC via USB, renaming the Windows.old folder to Windows, and renaming the current Windows to something else. My question is: Is that enough or do I need to edit any other files or folders? Thanks! Edit: I followed the suggestions provided here: First I tried F8 and Shift+F8 - no luck. Windows 10 just tried to load again and again. Occasionally I get a W10 BSOD with error WDF_Violation. Next, I used Hiren's boot cd miniXP to replace the folders in windows .old with those of windows 10. I saved the W10folders in a temp folder and rebooted. Windows 7 started to boot, but went into a BSOD/restart loop. I couldn't even see the message. So back to Hiren boot CD and reverse the process. Finaly I used Windows 10 Media (USB drive) to boot into setup , went to repair> Troubleshoot>Advanced options>Go Back to the Previous Build. Strangely there was only Windows 10 there. Clicked on that. It went into a screen "Restoring your previous version of Windows " but got stuck on "Restarting". After Googling it I realized I need to force a shut down for this to complete. After restarting, Windows 10 again tried to boot, went into the same BSOD as before and restarted. This time it completed the rollback to Windows 7! After checking that everything is working I used GWX Control Panel to delete anything Windows 10 on the PC, and prevent it from trying to reinstall again.