How to update IIS 6 to IIS 7.5 on Windows Server 2008 R2 Standard?

Solution 1:

IIS on Windows is version-locked. This means that 1 version of IIS ships with a specific version of Windows and that's it. If you want to change IIS, you need to change your version of Windows.

This matrix might help

IIS 5   -   Windows 2000 Server
IIS 6   -   Windows Server 2003
IIS 7   -   Windows Server 2008
IIS 7.5 -   Windows Server 2008 R2
IIS 8   -   Windows Server 2012

Generally speaking IIS Express isn't installed on a server, because there's no need. If you're working with an existing Windows 2008 R2 server that has the IIS (Web Server) role installed, you're working with IIS 7.5

Solution 2:

There is no IIS6 on Windows Server 2008R2, and it is not possible to install it there. So you already have IIS 7.5.

IIS 7.5 express is an application, not a service, it does not show up in Server Management, both Express and the full version can be installed at the same time. There is usually no reason to install Express on a server. It's used to development on workstations.