Photo files are a little different than music or video. Photos files are universal. Meaning they have the same extension whether its on a PC/Mac format.
If you have a jump drive/flash drive, format the drive on Mac. Then transfer the photos from your PC. Make sure you grab the photos and not just the info (txt). Then drag them into iPhoto.
Or you can save everything to a DVD-R and then upload from the disc to your Mac. This way you will have a backup copy of your photos. Its always recommended that you backup your photos to a disc. I like to backup to a disc because you can easily transfer to a PC or Mac.