I am trying to use a font in the Helvetica family for a Word document on a Windows 7 machine.
Why is the Helvetica font is not available by default through Microsoft Windows or Microsoft Office?
If you want to use Helvetica, you will have to buy it.
Helvetica is a licensed font family, any company wishing to use it must pay to do so. Windows has free-to-use alternatives such as Arial and Calibri but Helvetica is not freely available.
You can buy Windows TTF format fonts which will work with all applications, but anything you give to someone else will likely fall back to using Arial.