You have to put photo files in the same folder name as a camera does (on an SD card). It's 3:35 am and I'm in bed, so I can't check right now, but I think the folder has to be named DCIM or something like that. Also file names cannot be longer than 8 chars long, not counting extension. If not, iPad does not "see" the files on the SD card.
Afraid I can't help with syncing from PC to iPad. I know I can sync on the mac using iPhoto.
Just to add to the previous reply, you have to have a folder called DCIM off the root of the card with the photos beneath it, and their names have to be exactly 8 characters long (plus their extension).
If you want to copy them off your iPad and onto your computer then their is guidance here : http://support.apple.com/kb/HT4083