Despite having Avast antivirus installed and updated on his notebook, my son downloaded some type of virus or malware along with a software program he thought he could trust. The effects were the same as described here. His notebook would not load Windows Vista, even in safe mode. This HP notebook has a built in recovery drive but even that could not be accessed. The only recourse was a full system format and recovery using the back-up CD's that we created soon after the initial boot when the notebook was first purchased.
To boot from the CD we had to change the order of the boot options.
First turn off the computer.
Wait one minute before turning the power back on.
As the computer starts up, press the F2 key. (This might not work. For most computers F2 will be the right key but different computers may require the use of a different function key. We unsuccessfully tried F11, F2, and F8 before finding the right key for our notebook - F10. Each successive try will require you to turn off the computer and turn it back on until you find the right function key.)
As the Computer restarts, keep holding down the function key, watch for the BIOS Setup Message
Enter the BIOS Setup Utility (You may be offered other selections, such as "close." You don't want to close at this point. You want BIOS setup.)
Locate and Navigate to the Boot Order Options in BIOS
Make Changes to the Boot Order by moving Boot from CD into the first position.
Save Changes to the BIOS Setup Utility
Confirm Boot Order Changes and Exit BIOS
Insert the recovery CD.
Turn off the computer.
After one minute, turn the computer back on.
It will boot from the CD.
You will get a message asking if you want to "format and recover," "complete system recovery" or something similar.
Click "yes," "ok" or enter (whatever allows you to confirm this recovery action).
Your computer will begin the recovery process. This will take at least 20 minutes.
Check on it from time to time because you may be asked to confirm certain actions along the way for the reinstallation of drivers, original preloaded software etc. You will also be prompted when to insert the next CD/DVD, if you have more than one recovery CD.
When the recovery has been completed, you will receive a message on the screen to that effect.
Follow the instructions (for example: "remove CD and restart"
When your computer next restarts, it will be exactly the way it was when you first purchased it. You will have to reinstall (from CD or download) any software that was not preloaded and recover your documents, music and pictures from your back-up CD's, DVD's, thumb drives or external hard drives (where ever you store backed up files).
If you haven't performed regular back ups, you are out of luck because you will have lost all your files in the format and recovery.
If your computer did not come with system restore/recovery CD's or DVD's and you failed to create any yourself, you have a problem that is beyond the scope of my home user knowledge.