fagetti :
No please im here to help. You also used dmifit to inject serial number etc? I guess because it will give error on boot if you didnt.
Use only USB keyboard and test with bootable operating system like tails or ubuntu. If everything works fine then there was multiple problems with the laptop. Caps lock blink 2 times on this model is not OS related, i also never had 2blink because of defective keyboard but this could be first one.
You will get bios checksum error when you remove cmos battery and everything in bios goes to default settings, if it happens constantly and not only on your first boot after repair this means something else than that.
If you boot fast only with removed internal keyboard and with usb keyboard then it might be defective.
Download bootable LIVECD operating system, you can use USB or DVD to run it. Two linux operating systems i tested with are tails and ubuntu. Ubuntu is faster to get running. If everything is working well (use usb keyboard) with this operating system then your Operating system was corrupted and your internal keyboard is defective.
EDIT: battery might either be dead or something wrong with the motherboard / bios. Is it original battery?
Yes, I thought of using Ubuntu to test it.
I recorded the bios dump and booted the machine without the dmifit serial, is it necessary? It seemed to boot without it.
When I got the machine it had that caps lock flash 2 times then pause code, in the HP support page is classified as a bios corruption error and I started my trouble shooting based on that, after all this time I think is just a defective keyboard.
The owner is a headbanger drunk and he told me that now and then a "couple" of rum drops got into the keyboard, also when I took it was full of hair and dirt. That is why I think the keyboard shorted.
The COA sticker on the bottom case of the machine is broken and I don't have the key. I look for it on the battery compartment and is not there either.. I don't have the Win 7 Home Premium rescue disk, the owner never made them.
The machine had a free Win 10 upgrade so it must have a digital key but I don't know the Microsoft Account.
I will have to install Ubuntu, it's my best shot right now.
Do you think the Win 10 upgrade was the cause of the damage to this machine?
Thanx