gotcha!

found out what was happening! HD SC Setup didn't find my disk, so i
tried with another tool, vstformat (got it through download.com).
although it couldn't do anything with my harddisk, it fired it up (it
started making those offboard motor noises)! after that,
netbsd-installer had no problem whatsoever finding the disk.

for the moment it's installing stuff. if anything happens later, i'll
keep you posted.

pedro