Step 1. Unplug all USB devices and try again.
Step 2. Call HP for repair. HP is swapping motherboards on the 6000 and 9000 series a lot.
Extend the warranty on this one to the max.
The computer, a dv9233cl, will allow me to use the safe mode. I have tried to get help directly from hp's online chat three times but no fix. I have reseated the memory and hds and have restored the system to the orginal and still it will not work. Can anyone help me?