I DON’T want to stay logged on, but logging out does me NO GOOD!

I'm often away at my daughters (grand-parenting duties), and I use her PC (WIN7) to log into Hotmail (Outlook) .I've discovered that, even though I log off, my name and password are automatically filled when I go to log in. I have gone into Firefox options and taken the appropriate steps against cookies, caches etc; ditto Explorer and that dang autofill...STILL, every time I go to log in, I don't have to; all I have to do is tap the sign-in button! I don't have this problem on MY home PC - Please - help me stop this madness! Thank you.