After creating a virtual environment on win 7 (64bit) with:
py -3.7 -m venv venv

Running venv\Scripts\activate.bat will yield this result:
\Common was unexpected at this time.
(venv) C:\...

My PATH variable contains a path that starts with:
C:\Program Files (x86)\Common Files\...

To me this looks like this issue for virtualenv:
https://github.com/pypa/virtualenv/issues/35
https://github.com/pypa/virtualenv/pull/839

Running:
(venv) C:\Tools\venv_test>where python
C:\Python34\python.exe

This is my default python on PATH. Doing this with virtualenv:
(virtualenv) C:\Tools\venv_test>where python
C:\Tools\venv_test\virtualenv\Scripts\python.exe
C:\Python34\python.exe

I really hope this is not a duplicate.