I have Same problem. Im looking all over and the web is chock full of misdirection and bad outdated information. Ive spent hours.
I found a thread in the XAMPP for Windows forum that said to find php.ini
locate the line with extension=php_mssql etc etc, delete the semi colon and restart apache.
Now my apache won't restart, propbably going to have to re-install. My edit should have been done in pico or such, going to try that next.