I have just tried to install that extension on my dev server.
First, make sure that the extension is correctly enabled. Your
phpinfo() output doesn’t seem complete.
If you do not get that section in your
phpinfo(). Make sure that you are using the right version. There are both non-thread-safe and thread-safe versions of the extension.
Finally, check your
extension_dir setting. By default it’s this:
extension_dir = "ext", for most of the time it works fine, but if it doesn’t try:
extension_dir = "C:\PHP\ext".
EDIT given new info:
You are using the wrong function.
mssql_connect() is part of the Mssql extension. You are using microsoft’s extension, so use
sqlsrv_connect(), for the API for the microsoft driver, look at
SQLSRV_Help.chm which should be extracted to your
ext directory when you extracted the extension.