I think you need to keep tapping F8 only after power-on. Here is the procedure I had on file:
· Save all your important files.
· Unplug all the devices and drivers from your CPU
(except the keyboard and the mouse), including your printer, camera and memory stick.
· Shut off the computer and then turn it on, or simply restart it.
· As soon as you see the Dell logo at the start keep on hitting the F8 key repeatedly. Do not stop until you see the screen that says "Repair your computer." There will be other options too but chose this option and hit Enter.
· Next you will see a prompt window giving you options to select the keyboard layout select from the drop-down menu "US" and click "OK."
· On the next screen you will be asked to select the user ID and the password of your Windows
account. Select your user account, but make sure your user account has administrative functions. Type in your password. If you don't have a password, leave it blank and click "OK."
· Now you will come to a window with multiple options. Choose the one at the bottom that reads, "Dell Factory Image Restore." By clicking "Dell Factory Image Restore" , it will generate an operation that will take about 45 minutes to complete.