Thank you @TPFanatic
I don't know exactly what I did, but I got working. It seems that it doesn't start the first time, but it powers on after the third try. Maybe installing a new RTC battery will help with this, I don't know. Any ideas?
Here's some info:
BIOS 3.09 (7YETT79WW) - 2009-11-19
Embedded Controller 1.06
DISPLAY EDID: LP154WX7-TLP20
So you were right, the display is 1280x800 (the same as the one I already have on my T61) but it's actually very bright, and in great condition.
Now I have new problems as the fan is not spinning (the connector is broken) and it's evidently the wrong heat sink. It's not long enough to reach the chipset. What model is it for? Could you please tell me? Take a look:
I didn't hope for the motherboard to work but it looks like I got myself another Arch laptop. Now I'll have to find a WLAN card for it, a keyboard, and lots of screws.
By the way, is there something like a Middleton BIOS for this board?
I like the solid material of the display's cover case vis a vis the one the T61 has, which is soft and prone to marks.