Hi marcusd,

We'll be glad to try and help.
The more details you provide the easier it is for us to nail down a solution.
Based on what we know, I'd do the following.
Read through both links in my sig re: DMA and follow the suggestions.

Your optical drive(s)' transfer mode must be in DMA...something like UDMA 2.
It's not sufficient just to see "DMA if available".
The second link will have a VB Script file to fix this. I'd encourage you to read the whole article, it's not long and it's well worth the effort.