Hello Katy,
And thanks for your reply.
I already fixed my problem, but your reply is good to know.
In fact, i tried to install ArcGIS for SharePoint on a development machine, where Visual Studio (and its SQL server module) were previously installed.
After uninstalling Visual Studio, i was able to install ArcGIS for SharePoint. Then, the installation Visual Studio worked fine too.
Thanks for your reply again.
Régis.