If you try to install viflow the error"Unexpected error installing the package" occurs. The error code is 2739.
In order to install viflow, two Windows DLL files must be re-registered. Proceed as follows:
Start the Windows Command Prompt (cmd) with admin rights
Navigate to the directory: "C: \ Windows \ SysWOW64" (for 64bit Windows)
Run the commands: regsvr32 vbscript.dll and regsvr32 jscript.dll
Then, try to reinstall viflow 6.
There is also a Microsoft blog article on this topic.