In this article, they mention that the firmware inside the drive,
controls whether the cable interface is set to master or slave.
http://club.cdfreaks.com/f86/problem-nec-nd6750a-202674/
Rather than change the firmware, these guys butchered an adapter that
connects to the back of the drive, in order to control the mode it
runs in.
http://www.cubeowner.com/forums/index.php?showtopic=11665&hl=slave&st=0
Since your unit freezes when the boot starts, it could be caused
by both the hard drive and the DVD, conflicting on the cable.
There is a description here, of changing the drive from master
to slave, by flashing the firmware. The notes here say, that
the change only works one way, so you cannot change it back.
This is very dangerous. A soldering modification would be
safer.
http://liggydee.cdfreaks.com/page/en/Bootflash/
http://liggydee.cdfreaks.com/page/en/NEC-ND-6750A/
The trick then, is to figure out what the old drive was set
for, while it was in the laptop.
Before doing any of this, if you go into the laptop BIOS
screens, do you see both the hard drive and the DVD
drive, listed in the drives listing ?
I've never heard of this before. I only found this
information, while searching for info on ND6750A.
It seems a strange way to do something which is
so easy to do with normal jumpers on desktop drives.
And due to the danger, I'd want to see some evidence
that this is actually the problem.
http://club.cdfreaks.com/f86/toshiba-tecra-slimline-drive-replacement-204560
Paul