For Windows 7 64bit ONLY:

If during or after installation of Vectorworks, you see an error that claims the "VWPreview.dll" failed to install properly, you will need to download and install the following:
http://www.microsoft.com/en-us/download/details.aspx?id=14632
Then, run the Vectorworks installation again. The install should then complete properly. 
  Note: If you are using Vectorworks 2014, make sure to update to Service Pack 3 or later. This should also resolve the issue.