Creating Web App using an existing IIS Web Site

We can create a SharePoint Web Application by using an existing IIS web site.

The steps for doing this are:
1. Create a IIS Web Site
2. Go to Central Admin and select Create or Extend Web Application
3. Select "Use an existing IIS web site" and it will show all the web sites in IIS where SharePoint is not associated.
4. Select the IIS web site and SharePoint will be associated with this web Site and this web site and it will become web application in SharePoint terminology.

But what I am really interested to tell what difference comes when we associate the SharePoint to a normal IIS web site or remove SharePoint from an IIS Web Site.

When we have SharePoint Web App there are some special Sub Virtual Directories which are part of it. The directories are:

1. _vti_bin mapped to $localdrive$\Program Files\Common Files\Microsoft Shared\Web Server Extensions\12\isapi
2. _layouts mapped to $localdrive$\Program Files\Common Files\Microsoft Shared\Web Server Extensions\12\template\layouts
3. _wpresources mapped to $localdrive$\Program Files\Common Files\Microsoft Shared\Web Server Extensions\wpresources
4._controltemplates mapped to $localdrive$\Program Files\Common Files\Microsoft Shared\Web Server Extensions\12\template\controltemplates

so all of these directories are going to SharePoint. So if we see in IIS it looks like:



Now if we go to Central Administration and from Application Management select "Remove SharePoint from IIS Web site" option we will be shown all the web app. If we select this web app and continue the operation it will delete only these sub virtual sites. so lets see how it looks in IIS:



So when we create a Web application based on a IIS site or remove SharePoint from Web Application these are the virtual directories which gets affected.