intel bios update capsule header invalid

What's confusing me the most is that there are so many varied reports where some people use multiple different methods to successfully fix or bypass this issue, while there are also explanations of this signature/verification/etc that sound essentially impossible to solve. I need to decide whether I should abandon the Win7 install and revert him back to an HP Win8.1 install and do the OEM activation for that, or if there is some hope for this BIOS and activating Win7. I'm hoping to get more info on this as I've been at this for several days now and he needs the computer back ASAP. After some searching and a reply from BDMaster on here, I have a basic idea of what it is as far as security/verification and why it is problematic.

I had never heard of or encountered anything to do with the 'capsule header' before now. I've got a bunch of pages open and I've read lots of people talking about various methods, from using MMTool to simply extract/insert info from the original/modified ROMs, to using the undocumented /GAN command to force a flash of all blocks, to using UEFITool to do something with the capsule header (extract/insert, delete completely, etc), and lots more.

When I use the /GAN option, which is undocumented and is something I saw in a few threads regarding this issue (ex: SAFUWIN.exe BIOS.rom /GAN), it will 'complete' the flash but the next boot into Win7 shows that the SLIC info remains incorrect/incomplete when checked with the SLIC Toolkit. When I use the /CAPSULE option to attempt to flash the ROM and override the capsule header (ex: SAFUWIN.exe BIOS.rom /CAPSULE /B /P /N /K) it reports 'System BIOS image invalid or corrupt.' When I use the /D command to check the modded ROM file (ex: SAFUWIN.exe BIOS.rom /D) it reports 'ROM File Capsule Header checking. The SLIC 2.1 info per the SLIC Toolkit is incomplete/incorrect on HP's BIOS and thus Win7 is not activating. Using HP's latest BIOS download [h10025.(UEFI BIOS v8.19) and SAFUWIN.exe, AndyP's Phoenix Tool v2.57 identifies and successfully mods the ROM file, but HP's included SAFUWIN and several other AFU versions I've tried will not flash the modified ROM.

The system in question is a friend's HP Pavillion P7-1446s. I have not previously had an issue after many BIOS mods and flashes but am now very much stuck. First I want to say a quick thank you to all who contribute here as their work has been infinitely helpful to me over the years.

Intel bios update capsule header invalid