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You should not have a problem.
I'm running Civil 3d 2011, 2012, 2013 and 2014 on the same machine with no apparent issues.
How did your install go? I have had issuses with my Civil 3D 2013 ever since i installed IDSP 2014. Civil 3D 2013 starts up but sits on the "Loading..." phase forever until I finaaly stop it.