how to transfer photos from Windows to iPad

With the iPad attached to your computer's iTunes, if you select the iPad on the left-hand side one of the tabs on the right should be Photos i.e. in the same place as you chose which music, films, podcasts etc to sync to the iPad. There are instructions/help on this page : http://support.apple.com/kb/HT4236 . You need to sync all the photos that you want on the iPad together in one go, as not including photos in a subsequent photo sync is how you delete them from the iPad

In iTunes, select your iPad (under "Devices" on the left side) and then select "Photos". Click on "Sync Photos from" and then choose the folders that contain the pics you want to sync. You can not sync selected pictures - all the contents of a folder or none - but you can select multiple folders.