Home recording help (Magix). Track 1 bleeds onto other tracks.

not sure if this is the right sub for this question, but i've been really frustrated by this for a few weeks. i'll record or import track 1, and when i try to record the next track it records the input, plus the playback. i've messed with the input controls, stereo mix this and line in that, and nothing seems to work. i've used other programs before (older versions of magix, adobe audition, mixcraft), and never had this problem. using magix music studio on pc, windows 7. any help would be appreciated.