By default empty password should work: try mysql client in command line shell: $ mysql -uroot -p hit enter and enter (empty password).
Previous post may not seem obvious, but you actually have to hit enter
twice! 
In addition the mysql command line client, there is a mysql Windows service that needs to be running that the command-line tool is going to try to connect to.
Usually, the MySQL installer asks you if you want to start the service automatically, but perhaps this was missed. Check your Windows services in the control panel and make sure that a "MySQL" service has been started. If it's not even listed, then something went haywire during the install.
Jeff softiesonrails.com
I remember having this problem once a while back... I think I basically uninstalled MySQL, rebooted my Windows box, then re-installed. I'm not 100% sure that cured it, but it's worth a try, even though I know it sounds illogical.
There may also my a more detailed mysql log file somewhere on your hard drive, though I'm not exactly sure where it would be.
Jeff
Do you still have HeidiSQL running? Does it run on port 3306 too? If so, shut down HeidiSQL and try starting MySQL from the Services control panel. Sometimes the installer just fails at starting up the server, but if you go into the Services control panel you can sometimes start it up manually yourself (and then it should work every time you boot from that time on).
You could also try navigating a command prompt to your MySQL installation directory, and into the /bin/ dir and there try to run mysqld.exe, this may or may not occupy that command prompt for as long as you want the server running and may not give you any output. I've been running MySQL like that a while not too long ago (when I didn't want it as a service).
Hope that helps, Mathias.
