Assuming WindowsXP right click on the drive that corresponds to your
memory card, click properties, then the "Autoplay" tab and you should be
able to sort it from there ;)

Run /Applications/Image Capture
Open the Preferences dialog. Under the 'General' tab, there's an entry
which lets you select which application to open when a camera is
connected (which also includes cards connected via card readers). Change
it from iPhoto to No Application to have the OS just mount the card, but
not actually do anything with it.

-dms