In your my.ini have you got a server section looking something like this:
# SERVER SECTION
# ----------------------------------------------------------------------
#
# The following options will be read by the MySQL Server. Make sure that
# you have installed the server correctly (see above) so it reads this
# file.
#
[mysqld]
old_passwords # this or old-passwords seems to work
# The TCP/IP Port the MySQL Server will listen on
port=3306
#Path to installation directory. All paths are usually resolved relative to this.
basedir=D:/mysql/
#Path to the database root
datadir=D:/mysql/Data/
That's from my own my.ini file. If it isn't there just try throwing it in anywhere.
Mysql should be running as a service if you used the installer. First do ctrl-alt-delete to get the task manager up and see if mysqld-nt.exe is there as a process.
To restart it go to services (control panel -> Administrative tools -> component services) and have a look for mysql41.
Easy way to test if it's worked is to do
SELECT PASSWORD('foo'), OLD_PASSWORD('foo');
and see if they're both the same, and the first one isn't huuuge.