Installing on IIS 7/Windows Server 2008 R2/MSSQL 2008
phpmssql library missing


You are using the 8.x-2.x branch of the driver, that relies on a paid external library phpmssl:

http://www.drupalonwindows.com/en/content/phpmssql

You can use the "free" 8.x-1.x branch - that has no dependencies - for evaluation purposes. I say evaluation because it's a non supported half-broken branch I used to work on during the first D8 port attempt of the driver.

You can find full discussiones of this issue here:

http://www.drupalonwindows.com/en/blog/installing-drupal-8-windows

Disclaimer: I'm the maintainer for the SQL Server driver, PHP Mssql and Wincache.