Hi Peter - Thank you for your reply.  I've had a look at the page and it looks like it could fix my problem - but it doesn't say anything about xp x64, do you think that it would work with my OS??

Thanks again!

If you change to ATA mode, Windows will not boot without first installing the proper drivers and registry changes.  This information should help.  I tried it and it worked on my 9200.  However, I went back to RAID mode because of other issues with ATA mode.  IIRC, I didn't need to install the drivers from the MS website, but only needed the registry fix.

If you are operating in RAID mode, you need the RAID drivers! ATA mode is a simple backward compatible mode not intended to support RAID or other advanced features.

Peter 

I'm not sure about that.  You could try it, but I would back up the registry first.

Peter 

You know, back to your original assertion, which I meant to address but forgot:  You are trying to enable DMA for SATA devices.  I don't think you need to do so.  The fact that you can't do it doesn't mean there is a problem.  I can't enable or disable DMA for my SATA DVD drives or the controller.  But they work fine.

I think someone was giving you advice pertinent for ATA drives but not SATA.  You might be going to a lot of effort for no reason.

I wouldn't expect the ability to burn dual layer discs to be any different than single layer.  Can you burn a single layer disc?  If so, I think the problem is most likely the burner or the media or possibly the burning program.

You should test the throughput of your DVD drives to see if the data transfer rate is ok. Something like Nero CD-DVD speed is useful.  You can see how much CPU resources are needed to access the disc.  If not in DMA mode, it should be significant.  With DMA it should be small.

Peter 

I can burn a single layer disc successfully - first time, every time! To be fair, I have only tried one brand of dual-layer DVD [Datawrite].  But I was thrown because of the Device Manager, plus the fact that no flash utility will let me flash the firmware on my drive!  

I think the next thing should maybe be to try different discs?

Thanks for all your help! 

Just tried the Nero CD-DVD Speed test - The CPU Usage results were as follows:

at 1x: 10% 

at 2x: 8%

at 4x: 13%

at 8x: 23%

Yes, I would try a different disc.  There are also many firmware updates for burners to handle the many media out there.  One problem with Dell is that they don't issue many of the updates.

My CPU Usage numbers (D9200 with Q6600):

1x: 3%

2x: 7%

4x: 13%

8x: n/a (disk didn't have enough data)

They look pretty similar to yours (ignoring 1x which looks odd for yours). 

Peter 

Yeh - after looking at yours, 1x does seem odd - especially given that I have the same processor as you!  I will try another Dual Layer disc - maybe made by Verbatim or another reputable company - and post on here when I have done so.

Thanks for your help. 

Your CPU might have been busy doing something else when doing the 1x test.  I wouldn't worry about it.

Peter 

yeh you're probably right.  I'll post when I've bought a new dual layer disc from a different brand.