Lost photos, copying error. Please help?

Hi,
I just did something really stupid! I wanted to copy a large folder of pics to an external hard drive. I had already an incomplete version of the folder on that hard drive. My mac asked me if I want to replace or merge or stop, I click replace... That's when I realized I was copying the wrong way, from the external to the Mac!!! Argghhh. I click cancel and now I only have the incomplete folder on both drives :-( Any way to get this back please???

It sounds like you over wrote the original folder on your Mac with the incomplete folder which will make recovering the photos almost impossible. First verify that in fact you have the incomplete folder on your Mac rather than the original you were copying from. If that's the case, hopefully the photos are still in your camera or on a SD card where you can again copy them from.