Disappearance

Hello. I recently bought a SSD: Kingston SA400S37/240G (C: ) and I'm using it along with a Toshiba DT01ACA100 that has two partitions (D: and G: ). Before the SSD i only had that Toshiba and had no problems. Since i have both, the HDD disappears when its being used. I have Windows + 1 game on...