(it tells me: "ERROR LOADING OPERATING SYSTEM)
Where did you buy it? L
Did you make the recovery disk set when you got the machine? If so there is an option in the installation process that allows for windows repair. Failing that check out this URL http://h10032.www1.hp.com/ctg/Manual/c01035677.pdf go to the section entitled "Recovering from the Partition on the Hard Drive" that should help out. If all else fails & your hard drive is completely shot you will have to install a new drive & re-install the OS, your machine should have a Windows sticker on it with the version & activation code, you will need a Windows disk with the same version to re-install with that number THIS IS NOT PIRACY Microsoft don't give a monkeys where your disk came from so long as it is the same version as the one you have a licence for on the machine, if it's not the same the activation key won't work anyway. I have done this dozens of times without an issue I have even called Microsoft support on a couple of occasions when the OS has been installed on the same machine a few times & a message came up to contact them, I have told them on at least three occasions that the disk was not the one provide with the machine but was the same version & they have always allowed the install.
Check to make sure its not trying to boot off of something else. A bootable USB drive that you leave plugged in will cause the BIOS to try and boot from it and when it finds no OS on it you will get that message. It could also happen with a CD or DVD although usually it will skip those if it finds no OS there. And another thing would be an external drive left plugged in, especially a SATA drive. You may have to check the boot order in the BIOS to make sure its not going to the wrong drive. So everything might be just fine, but its just looking at the wrong drive to boot from. I have actually seen this a lot and it really panics people because they think they have lost all their stuff. So when someone calls frantically for for help the first thing I have them do is make sure everything is unplugged, especially USB pen drives.
I'm no expert but "error loading operating system" sounds like either there is something wrong with your harddrive preventing your system from reaching the OS or there is a problem in the OS software itself. I would suggest trying to reinstall the OS. Starting up with the windows cd should indicate if there is a problem with the harddrive (in which case you probably need a new one) and if that is not the case you can reinstall windows itself.Hope that helps