Welcome to the HTG forums!
Your hard drive may be faulty. You could try to check that by using an Ubuntu Live CD. You can use a Live CD to access Ubuntu on your computer without installing or changing anything. You can download the ISO image of Ubuntu Live CD from http://www.ubuntu.com/download/desktop . Select 12.04 (32-bit version). Burn it to a CD or DVD with ImgBurn www.imgburn.com .
To boot from the CD or USB via the "Boot Menu" you may need to press ESC or F9 during the HP screen when you turn on your computer. Then select your CD / DVD device to boot. Once the installer shows up, select "Try Ubuntu".
You will be able to access the forums with your PC using Firefox in Ubuntu. Once you get to the Ubuntu Desktop, select the "Dash Home" icon on the top of the launcher.
Then search for "Disk Utility".
On the left, select your hard drive, and then check the disk's "SMART Status" and click on "SMART Data".
Check the SMART Data for any problems.
If you have trouble booting into Ubuntu try again, but this time, when you boot from the CD/DVD, you will first see this tiny logo at the bottom of the screen:
At this point you must press a key, ENTER for instance. You will be presented with a list of languages, English is already selected so press ENTER. Then you will see this:
Press F6, and go down to "nomodeset" by pressing DOWN ARROW.
Press SPACE, the "nomodeset" option will be selected.
Press ESC, the menu will close.
Press ENTER to boot into Ubuntu.
If you have any trouble please ask us.