computer wont run 3 hard drives at the same time

[DukeDaGod]

i have windows 7 and i was running 2 hard drives fine so i decided to run 3 but when i installed the third 1 my second 1 dissappeared and the third 1 became my second 1 when i unplug the new 1 my old 1 shows againe someone please help i wonna run 3 hard drives