Hi, thank you for contacting JustAnswer.com. My name is Russell. I will do my best to provide the right answer to your question.
Given that you have an SATA hard drive, you may require a special SATA driver for it, in order for Windows to get past the initial bootup-attempt-to-load-Windows message.
It sounds as if you formatted the SATA hard drive "from another laptop" on
another laptop first, before putting it into the HP Envy dv7... is that the case? if so, that could be a mistake, also. Try formatting it in the HP Envy, if at all possible.
This page from HP's support website/forum starts out saying that this model (Envy dv7) won't have Windows 7 drivers released for it unless the model of NB (notebook) is ever issued with Windows 7... but later in the page there are some detailed instructions that may be N/A to your case... since you can't even boot up ... but which might contain something helpful to your case also:http://h30434.www3.hp.com/t5/Notebook-Operating-Systems-e-g-Windows-8-and-Software/Drivers-for-Windows-7-Laptop-HP-Envy-dv7-7255er/td-p/2327647
Particularly, there are some links there, to software packages appropriate to this laptop that can be put on Windows 7 once it is installed. Perhaps they can be put on the hard drive you use, when it is booted up on another machine?? once it has Windows 7 installed.
But, I suspect that getting the proper SATA driver configured for the hard disk itself, or just formatting the SATA hard drive on the Envy dv7, might be the real solution, even if it sounds simple.
Is there an objection, such as that the Envy dv7 lacks a CD/DVD disc drive? if so I'll see if I can guide you through that problem also. So let me know the details relevant to the issues I have raised and the advice I've given, and I will try to guide you further through the process to a good conclusion.