You probably need to repair the ME firmware. Since you have ME6 1.5MB firmware, you need to use Intel ME System Tools v6 1.5MB/5MB. Use Flash Programming Tool with command "fptw -greset" and after the restart run MEInfo tool again from the proper System Tools archive. Also, try the command "fptw -d spi.bin" and let me know what it shows.

That model has two SPI chips, 2+2 = 4MB. The first chip (W25Q16BV) holds the Flash Descriptor + ME region whereas the second (EN25F16) holds the BIOS. FPT detects only W25Q16BV because the Flash Descriptor shows that the BIOS is missing. That should be by design from Acer, I assume because they use their own flasher to update the 2nd chip which holds the BIOS. Their own BIOS updates only include that 2MB chip's image as well. It doesn't really matter to us though as we need to work on the 1st chip which holds the ME region. The problem is that your ME region is read/write protected so we cannot fix the problem easily. Download the attached DOS executable and run it with parameter "-e:glow" followed by "-e:reboot" once the first is complete. Upon reboot, does FPT still show Error 26? If it doesn't, compress and attach resulting "spi.bin" image here. If that fails, do you see any interesting option at the BIOS to disable the ME or similar? Something like ME Disable, Enable ME Reflash, HMRFPO etc. Do you have a hardware programmer and chip soldering knowledge?

It should work from the next reboot, not right away. The reboot command of sprom didn't do anything apparently, hopefully the first does work though. Rename the executable to sprom.exe (to avoid typing the tilde ~ every time) and after the glow command run "fpt -greset". Check again after the reboot if you can dump via fpt.

Try the opposite command, meaning "-e:ghigh". Other than that, you'll need to answer the extra questions from post #5.

The old chip is not useful, unless you just want to experiment on it first with the programmer to see how the procedure unfolds.

The chip you need is W25Q16BV and the name is right on top of it so you should be able to find it easily. You can find some pictures online to see what you are looking for. We don't need the 2nd chip dumped since the ME firmware is found at the first only.

Once it's desoldered, does your friend also have a programmer? If not, you can buy a cheap one (CH341A for example) and a SOIC8 clip.

Once you have dumped the chip, compress and attach it here.

The problem usually lies with the motherboard/chipset change (wrong Initialization data, see Section A). The old chip comes from another motherboard, the new motherboard should have worked on its own. You can try what you suggest. Usually though, when someone goes through all the trouble to desolder and resolder a chip, it's common sense to spend some time to just fix the SPI image before flashing back. It's up to you and the tools you have for the job. Try what you suggested but if it doesn't work you'll need to get a programmer and redo the soldering.

The chipset/PCH SKU may be the same (HM55) but the actual silicon is not. The ME co-processor is inside the PCH and that's why the Initialization data are important in such cases. The BIOS is not static either even at a different system of the exact same model/SKU. What you suggest might work, it might not. You'll know if you try only. You can also search online for other Acer "sprom" versions from other systems just in case something works for you but that will take time even if you find something that manages to unlock the FD.