Unable to install OS on Elitbook 8440p after Disabling Drivelock

Question

Good Morning. I have two Elitebook 8440p computers and I noticed on two of them. When i disabled drivelock and anti theft and attempted to boot it up the machine stays stuck on "Starting Windows".  I have attempted the following support steps
1. Tried re-enabling drive lock as well as anti-theft and also tried resetting BIOS to defaults.
2. Using the disk sanitizer and secure erase on the hard drive
3. Tried booting using a Windows 7 64 Bit USB stick to attempt to install a new OS. It does the same thing. Get stuck on Starting Windows.
4, Tried switching Hard drives from other HP Elitbook 8440p machines.
None of these support steps resolved the issue. One thing I do notice on the machines experiencing the issue that other machines aren't. When I select to boot from USB it does not say "Press any key to continue". It simply goes to Loading windows files then hangs on Starting windows. On other identical machines it asks to press any key to continue.  Please let me know if you require any information from me to help resolve this. Thank you.

Answer 1

How to Clean Install Snow Leopard
Be sure to make a backup first because the following procedure will erase
the drive and everything on it.
     1. Boot the computer using the Snow Leopard Installer Disc or the Disc 1 that came
         with your computer.  Insert the disc into the optical drive and restart the computer.
         After the chime press and hold down the  "C" key.  Release the key when you see
         a small spinning gear appear below the dark gray Apple logo.
     2. After the installer loads select your language and click on the Continue
         button. When the menu bar appears select Disk Utility from the Utilities menu.
         After DU loads select the hard drive entry from the left side list (mfgr.'s ID and drive
         size.)  Click on the Partition tab in the DU main window.  Set the number of
         partitions to one (1) from the Partitions drop down menu, click on Options button
         and select GUID, click on OK, then set the format type to MacOS Extended
         (Journaled, if supported), then click on the Apply button.
     3. When the formatting has completed quit DU and return to the installer.  Proceed
         with the OS X installation and follow the directions included with the installer.
     4. When the installation has completed your computer will Restart into the Setup
         Assistant. Be sure you configure your initial admin account with the exact same
         username and password that you used on your old drive. After you finish Setup
         Assistant will complete the installation after which you will be running a fresh
         install of OS X.  You can now begin the update process by opening Software
         Update and installing all recommended updates to bring your installation current.
Download and install Mac OS X 10.6.8 Update Combo v1.1.