Upgrading from:

Calculus`FourierTransform`

The symbolic functions in Calculus`FourierTransform` have been added to the built-in Mathematica kernel.
The numerical functionality in Calculus`FourierTransform` is now available through the newly created Fourier Series Package.

To access functionality from the new Fourier Series Package, load FourierSeries`:

Version 5.2 << Calculus`FourierTransform`

This gives a numerical approximation to the Fourier transform of Exp(-t2)/(1+t) with respect to at :

Version 5.2 NFourierTransform[Exp[-t^2]/(1 + Abs[t]), t, 1]