Never mind!!! An adapter/tray was in the way. (The four pins by themselves are not connected.)
NOT TRUE!!! For example, http://www.newegg.com/Product/Product.aspx?Item=N82E16817145136 (VANTEC NexStar3 NST-260U2-BL)
is specified as an external hard drive enclosure for a 2.5" IDE drive, but the internal IDE connector in this product cannot begin to connect with the ATA-6 (Ultra ATA/100) 2.5" IDE drive I have (Hitachi Travelstar 7K60 [model: HTS726060M9AT00] seen at http://www.hitachigst.com/portal/site/en/menuitem.5b9d7243bfa3d65befca8644eac4f0a0/ ).
I have not yet found a drive enclosure that will work with my ATA-6 2.5" drive, it appears the "Cables To Go 35559" may be discontinued. I will respond here if I find one.