how to make an image of /dev/sda1

[Lenny]

Hi,
I have a clean copy of XP on my Asus 701 on /dev/sda1.
I want to make an ISO image of it before installing Linux onto it.
I am trying to use the DD command and I keep getting errors, like "file does 
not exist".
I type using sudo of course:
dd if=/dev/sda1 of=/dev/sdd1/xpfile.iso
I have tried just /dev/sda and /dev/sdd0 and 1.
/dev/sdd is my 4 gb SD card.
Thanks for any ideas.
Glenn