Too slow CD-ROM-speed

[FinalFn]

I've got a 40x (16x DVD)-ROM but it only reads NORMAL (no copy-protected or audio) CDs with 4x - why?
DVDs are only read with 2x

What exactly do i have to do to make my CD-ROM-drive running in normal speed?

[It's an ATAPI DVD-ROM - i've got the normal WinXP-drivers installed]

[ya_jai]

Make sure you enable DMA for this drive. Goto control panel--> System --> Hardware --> Device Manger --> IDE ATA/ATAPI Controller then select where your dvd rom is (Primary or Secondary), then in advance tab select DMA if available.

[FinalFn]

I switched my DVD-ROM to "DMA when available" but now there is written "used mode: PIO-mode" - at my CD-Recorder is standing "Multiword DMA mode 2" (the CD-Recorder works in right speed)

What can i do to make my DVD-Rom working with DMA?