Thanks a lot. You saved my day. I was tearing my hair over this. Never occurred to me that clearing the version could stop ISS from registering. By the way I'm using Installshield 2015 - (project upgraded from 2013) I have tight timelines for development & delivery, Installshield is a real nightmare! Thanks again davidg wrote: Thought I would post the work around so when someone else runs into this they will have a solution. Here are the steps that allowed me to avoid this: [LIST=1] Clear the ASP .Net version property from the Virtual Directory. This will turn off the unwanted call to aspnet_regiis.exe -s W3SVC/1/Root/. Create a custom action that calls the same logic but includes the full path to the application (eg. aspnet_regiis.exe -s W3SVC/1/Root/MyVirDir) I still don't know why this is being called. This is not desired on the root of the website. If a company had 100 .net 2 virtual directories under a website they would all be set to .net 4 because I deployed a virtual directory. This is very bad and takes time to set them all back, as well causes downtime to sites that are not compatible with .net 4. From the aspnet_regiis documentation: Note: This Issue also exists in Install Shield 2012. ... View more