This will most likely only work if you have cookie nabled on your computer though and you don't have a pop up killer enabled.....and considering the site is riddled with them I would highly recommend putting up with signing in to live without the hassle of those.
Click in the box where it says Enter Your Username - your name should already be there now, so just click on your name.
Go to Tools - Internet Options - Content, select Auto Complete. Check the box that says 'Prompt me to save passwords'. That's it, you won't have to type them again.