First, click on FILE on the top left of the screen, and click Preferences. Select the DEVICES tab and check the box before "Prevent iPod, iPhones, and iPads from syncing automatically." Open iTunes with your iPad attached and in the left hand column under devices, select your iPad, a Summary window will open.
Second, you should remove the pictures currently in the Camera Roll (Photos), you can do this by unchecking the "Sync Photos from My Pictures" and syncing, this will remove all pictures from your iPad so you won't be duplicating everything. You need to setup a folder, on your PC under "My Pictures", such as, "iPad Pictures" and make all of the folders you want, with the pictures you want in them (copy, move or drag and drop, your choice), under that folder. Then go into iTunes, under PHOTOS and select "Sync Photos from" and change "My Pictures" to "Choose Folder" and then choose the folder you created "iPad Pictures" open it and select the folders you want to sync to the iPad. Then sync them.
Keep in mind that if the things you want to transfer aren't checked it will remove them from the iPad!