If you are concerned about someone getting your password: do not use auto sign in, just delete the login list (start > run..type: control userpasswords2 <enter>, advanced tab..click manage passwords button and remove all passports listed). Just log in with your password everytime.
What's not stored on your computer can't be retrieved that easy
Also do a Ad-/Spyware check and check programslist for any programs you didn't install.
/ 
