Ack, a windos box
My background is MySQL under Linux (RedHat) Hmmm... I guess the commands will be the same I will just need to figure out how the command lines differ in the executable.
What version of Windows server is this btw?
Have you run winmysqladmin? The first time you are asked to create one user that is admin/root.
Lets go back and check permissions...
restart MySql server with --skip-grant-tables
Login to mysql --user=root
select * from mysql.user
check that 'admin' is there with a correct password set AND FOR Host='localhost'
if yes, then you mistyped your 'admin' password. Change it.
if not, then change the 'admin' entry:
update mysql.user set Host='localhost',Password=PASSWORD('youradminpassword') WHERE User='admin';
flush privileges;
exit;
Now try restarting MySql server normally. Let us know how this goes...