Thanks for the replies.
"dmesg | grep DMA" gave the following output:
SIS5513: SiS 962/963 MuTIOL IDE UDMA133 controller
ide0: BM-DMA at 0xffa0-0xffa7, BIOS settings: hda
ide1: BM-DMA at 0xffa8-0xffaf, BIOS settings: hdc
hda: 234441648 sectors (120034 MB) w/2048KiB Cache, CHS=14593/255/63, UDMA(100)
It looks as if hda (my hard drive) is running in DMA mode. Is that right?
EDIT: I don't have a clue what the smilies are doing in there but I can't get rid of them!