Technically, running on Parallels or BootCamp is not a supported platform for Orca3D, however we do have users who have successfully used both programs, but there appears to be an issue using Parallels with Windows 7.
When Orca3D installs, it checks that support files are installed and if not tries to download them. Is it possible your internet connection is being blocked during the install? One other option is to download and install the necessary files before installing Orca3D. The most common file missing is the Microsoft Report Viewer which is used to create reports in Orca3D. You can download this file from Microsoft here: http://www.microsoft.com/download/en/details.aspx?id=3841
Please let us know if you continue to have problems.