Ok, did a few more tests!

I removed the external termination and it booted up to almost the end on the internal HD, but the computer freezes just at the boot end.

The HD is a Quantum 730 Mb (LT73S0011 or something like this). I did not had more time to test anything else...

So far, I did not see any jumpers on the hardrive itself... Maybe I did not looked correctly, bit normally they are obvious...