You may be able to launch Factory Restore. You will be able to save files also - see below "a prompt to backup the user files before beginning the recovery is displayed."
Restore the PC to its original condition with the HP Recovery Manager if Windows Vista is not accessible
If the PC cannot launch into Windows, it may still be possible to use the HP Recovery Manager on the hard drive to restore the computer to its original operating condition. The Recovery Manager can be launched during the start up process by following the steps below.
Press the Power button to start the PC, and then press the f11 key when the standard BIOS prompts are displayed on the black screen.
NOTE:Pressing the F11 key during the startup on a computer with an HP factory image will start the system recovery process even if the prompt is not displayed.
If the HP Recovery Manager can access the recovery partition on the hard drive, a prompt to backup the user files before beginning the recovery is displayed. Follow any on-screen instructions.
If the HP Recovery Manager cannot access the hard drive to fix any system errors, you will need to use the personalized recovery disc that you created to recover the hard drive to its original condition.
If you have not created the personalized recovery disc, or the discs are corrupted, you can order a replacement recovery disc from HP.
When the Recovery Manager starts, follow the step-by-step recovery instructions shown above.