Hi
Microsoft still has Windows 7 iso for download but only retail versions and only if you have a retail key available to allow the download to proceed
you can choose language/country home or pro and 32 or 64 bit
you must chose Home or Pro matching your windows key but 32 or 64 choice is yours
(depending on amount of RAM minimum 4GB for 64 bit version)
Ideally you want the updated version after 7 SP1 which allows a key from 7 or 7 with SP1 included to activate the install
otherwise W7 SP1 key does not work on original W7 and key for W 7 does not work on W 7 inc SP1
I Googled
windows 7 sp1 iso site:microsoft.com
and got the UK english page
https://www.microsoft.com/en-gb/software-download/windows7
dont download from any one else other than Microsoft to ensure there is no added malware
It is possible that HP can provide an OEM version of Windows 7 specifically for HP systems
regards
Mike Barnes