Installing Gallery 2 on IIS in a hosted environment is not possible, unless you have local administrator permissions on the server.
Operating System: This guide assumes that you have Windows Server 2008 or Windows Vista SP1. These operating systems include FastCGI out of the box. FastCGI was also back-ported to IIS6 (Windows Server 2003) and you can download out-of-band release of FastCGI for IIS7 (Windows Vista).
SQL Server: Download Microsoft SQL Server 2005 Express Edition from http://msdn2.microsoft.com/en-us/express/bb410792.aspx
Unless you use third-party tool, I recommend that you use Management Studio Express which is installed if you download Microsoft SQL Server 2005 Express Edition with Advanced Services.
PHP:
Please follow the instructions from http://learn.iis.net/page.aspx/246/using-fastcgi-to-host-php-applications-on-iis7/ and install PHP as FastCGI application. Additionally, in IIS Manager click on Default Document and add index.php to the list.
In this guide we use "gallery2" as the database name for your gallery, you can choose another if you want.
