I’m a first time user of Cubase using Cubase 6. I’m trying to record vocals through a mic connected to the mic in on a Creative Soundblaster X-fi Titanium HD. The audio track records everything, metronome, bass and other vocal tracks. What am I doing wrong?
Do yourself a favour and get a dedicated audio interface. Stuff suited for audio production way better than anything Soundblaster is available for little money.
Nonetheless you can try to sort out what audio is played on what channels. First in Cubase get into the devices menu > VST-Audiosystem and assure you have an ASIO driver installed for the Soundblaster (ad says ASIO 2.0 is supported). Then press F4 (VST connections), create one or more input busses and see which and how many device ports are displayed. Choose the one your mic is connected to and rename the bus to ‘mic’. Be sure your recording channel’s input shows ‘mic’ in the mixer.
Good luck 
Also look for something like “what you hear” or similar in your creative setup and switch it off!!!