This means that the computer is not finding something to boot up off of. Like your hard drive.
Contact HP or you can check to see if it will boot off of a CD like a windows cd.
If so, then the hard drive either crashed or the bios is set to boot off of something other than the hard drive. For that you can change the boot order.
To do that you'll need to find out how to get into the bios for your Motherboard. In the Advanced options you can find the boot order. Just make sure the hard drive is selected.
If it still does not work, you'll need help with changing it out and installing the Operating system.
Contact HP or you can check to see if it will boot off of a CD like a windows cd.
If so, then the hard drive either crashed or the bios is set to boot off of something other than the hard drive. For that you can change the boot order.
To do that you'll need to find out how to get into the bios for your Motherboard. In the Advanced options you can find the boot order. Just make sure the hard drive is selected.
If it still does not work, you'll need help with changing it out and installing the Operating system.