Hello @Ballfat
Welcome to the HP Support forum. Thank you for posting.
This PC model originally comes with Windows preinstalled by HP (a.k.a. OEM Windows). Therefore if you need to reinstall Windows, your best path is using original HP Recovery media - it contains genuine Windows, drivers and certain preinstalled apps. The one for your model is this one >> http://www.computersurgeons.com/p-20692-recovery-kit-679965-001-for-hp-pavilion-notebook-pc-model-nu...
I guess that your Windows 7 installation media may be corrupt or could have been "touched" by unauthorized parties - it should recognize any HDD just fine. You may also check your BIOS settings and ensure they are all set to default condition.
I recommend you use the recovery media to restore the PC to factory default condition. Once you receive it at home, here are detailed instructions how to use it > http://hp.dezide.com/ts/start.jsp?guide=HPSystemRecovery.net&as=true§ion=ccweb&SFS=tdoc&language...
Hope this helps. Let me know if you face difficulties.
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*** HP employee *** I express personal opinion only *** Joined the Community in 2013