I am having troubles reading DVD's on my NEC4551a driver.
The drive itself start spinning fast and loud then I can hear a few clicks (from the DVD or from the Hard Disk?) and then the system hangs completely: first the icons start disappearing then explorer. There is no mouse/keyboard control; so I have to resort to a reset.
When the system reboot the bios shows that the Sata HD isn't recognized at all?! And then reappears only after a complete shut down.

The system comprises of 1 DVD writer and 1 CD writer each connected to their own ata (EIDE) socket as masters.
There are 2 sata HD connected to their own sata sockets.

I've done some search and found some clues related to a possible PIO reset due to bad quality DVD media...but I've checked the IDE controllers and correctly say UDMA2 selected.

I believe the problem is confined to the NEC4551a since it persist even when trying to install XP or other OS's (e.g. Suse10) using a bootable DVD instead of a CD.

I've downloaded a few firmware but not really sure if that would solve the problem...and don't want to loose the warranty by just experimenting with them.

Almost certainly a driver conflict if it only happens in Windows. If it also happens in DOS then maybe it is the drive itself. Firmware won't fix that.

In Windows, make very sure that ONLY the default Windows IDE controller driver is in use. As a test, try disabling auto-run and see if it still does this.

Thanks for your reply.
driver conflict? I doubt as I've never installed any IDE driver, so the only one working must be a windows one.
In fact, as I've installed Suse on another partition, I might just as well try to read a DVD there...
but as I've explained, it seems this is a DVD driver (NEC4551a) problem as sometimes I cannot install OS's (so from DOS).
I'm also going to swap IDE connections between the CD writer and the DVD...to check if there is any cabling problem.

Thanks for any suggestion.

Well, I've tried to read lots of DVD's in Suse10 and no problem at all.
It looks as the NEC4551a works fine.
A quick check on DVD's using Nero tools shows that some DVD had some bad clusters.
Also I managed to install another instance of XP64pro using a bootable CD from the same drive. So it really is between Windows and NEC.

What firmware are you using? The latest official is 1-08... try to uninstall IDE drivers in Windows and detect them again...

SOLVED! at last...
It took a while but the problem is now gone forever.

It was nothing to do with the NEC writer nor with any driver issue.
In fact a further testing session using SUSE (linux) reported the same problems encountered in Windows so it was a Hardware problem (Linux was simply more tolerant and took longer to crash...but I've found out about this later).
It was a defective IDE cable which I've tested on others IDE sockets and a CD writer, resulting in ugly crashes wherever and whatever that thing was connected.
I've removed that garbage from my system and everything is smooth as it should.

I bought that "infected" cable at one boot sale....I should have known better.

Thanks for posting problem solved.