Vivado can't start

[blueskull]

A real beginner's question here...
I just got my CMOD-A7 and I'm trying to get some weekend fun project done on it.
The first problem I encountered is Vivado. After downloading 3GB of archives, Vivado finally installed, with an error reporting VC redist is not properly configured.
I ignored it and finished the installation. On first launch of Vivado, it reported the same bug and can't be fixed.
I then uninstalled all same version of vcredist (2015) from my computer and let Vivado install its own, which succeeded.
Upon next startup of Vivado, it still requested me to repair vcredist, which I did a few times, and still, no help.
After following a post on Xilinx website, I renamed vcredist installer and this time there's no nagging anymore, but Vivado still can't start.
A few tens of seconds later, a window popped up with "Error when launching 'C:\Tools\Vivado\2017.1\bin\vivado,bat': Launcher tine out".

Now, what to do? Any help is greatly appreciated.