Civil 3D 2015 is a 64-bit only application. It will not install on a 32-bit operating system.
Ensure that your system meets the minimum requirements for running AutoCAD Civil 3D 2015, which typically includes a multi-core Intel processor, 8 GB of RAM (though more is recommended), and a compatible graphics card. autocad civil 3d 2015 15
if you want to pull heights from an existing surface or manually input them. 2. Draw Manually Civil 3D 2015 is a 64-bit only application