Assuming (1) you can turn off UEFI and such, (2) HP has Windows 7 drivers for you to download and (3) you don't mind your warranty (on software issues) being voided, any Windows 7 install disk would be fine.
But it's much easier to download Start8 or Classic Shell and make Windows 8 look and behave like Windows 7.
Kees
I purchased a laptop (HP) with windows 8 loaded on it. I find it hard to use and would like to use Windows 7 instead. What kind of disk do I need to purchase to enable it to load and run successfully. Also this laptop does not have the touch screen.

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