MySQL Error Nr 1045: Access denied ... (using password: YES)

If you opt to reinstall MySQL, the following error is probably what you'll find upon reinstalling and finishing the MySQL Instance Config Wizard:

The solution is to not only uninstall MySQL, but also remove (a) the directory where it is installed, and (b) the directory where it keeps its settings. On Windows 7, the latter can be found at C:\ProgramData\MySQL, or C:\Users\All Users\MySQL which is the same thing. Once these are removed, proceed to reinstall MySQL, doing a detailed configuration (from the MySQL Instance Config Wizard) to reset the root password. If you miss any of these steps, you might need to uninstall and reinstall again.