How to install Windows 7 Pro back onto HP z420 workstation

[Johnathanrm]

good evening everyone my issue is that I have a HP z420 workstation with a pre-installed Windows 7 Pro downgraded from Windows 8.1 and I am replacing the hard-drive from scratch I have a new drive and I don't have a backup or installation media. When I go to the Microsoft support page and enter the product key they say to go to hp's website since this is a pre-installed key so I cannot download the iso directly from Microsoft as I could with Windows 8. 

If there could be any support related to that then it would be wonderful.

EDIT: I ended up trying a Windows 7 pro install disc that I borrowed and when I'm at the part where I select the disk drive I have none come up as available. The BIOS is set to factory defaults and I have attempted to boot up the windows 7 copy from both a disc and a USB boot up configuration and still get nothing even after I try to load the chipset drivers from the HP support site I just get a message informing me to load a signed driver 

UPDATE: I've finally done it! I went into the BIOS and changed the option from RAID+AHCI to just AHCI! I'm so relieved that its finally working 🙂 Thank you again for your time 🙂

[Paul_Tikkanen]

Hi:

See if this works...I have zipped up and attached the storage controller drivers below.

Use the DVD or put the USB flash drive into one of the USB 2 ports.  It won't work from a USB 3 port

Unzip them and copy them to a USB flash drive.

Unfortunately I don't know exactly what storage controller driver you need, but you can browse to each folder using the Load Driver option during the install.  Check the box, and it should only include the compatible driver.

One of those folders should have the correct storage controller driver.

[Johnathanrm]

Thank you Paul for the reply, unfortunately when i try that i get the following error code. (this is a screenshot i found on the internet but same message comes up) When i try finding the windows 7 32 bit drivers i then am able to see the disk drive but then get the error about being unable to create or locate a partition.

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[Johnathanrm · Accepted solution]

I've finally done it! I went into the BIOS and changed the option from RAID+AHCI to just AHCI! I'm so relieved that its finally working 🙂 Thank you again for your time 🙂

[Paul_Tikkanen]

You're very welcome.

Glad you got Windows to install.

[brighstar]

Hi Paul,

My Windows7 still does not recognize those drivers you gave.