I am running windows 8.1. my issue was resolved due to my own research.
Some helpful guy wrote this above and it is marked as 'solved. I use some extra keywords in this text so hopefully you will find this solution sooner. I have solved it and did not need to send the PC in for repair.
HP Envy m7 stopped booting after a week or so. You tried the hard reset, reseated the memory etc, but it did not work.
The problem is caused by an automatic update with the latest but corrupt BIOS file from HP.
This will stop the 2x4GB pc3L 12800S DIMM to work, causing the screen to go blank, with not even a splash screen so the PC is inaccessible.
In order to access the PC you will need a 1 or 2 GB single DIMM pc3-10600s or 8500s.
Remove both 4GB DIMMs and seat the smaller and slower DIMM in one of the banks. Please note that only one of the two banks will work, they do not work simultaneously anymore and also note they can not read RAM above 2GB.
The PC should now boot
Download the latest BIOS driver from HP, - yes the same corrupt one-, and do a manual BIOS update to overwrite it with the same file.
After the restart to complete it, the PC will reboot again because it now recognizes the corruption and will revert back to the default settings. Complete the process and switch back to your 2x4GB RAM and it will work as before. Good luck
W.