Have you thought of your computer keyboard keystrokes being recorded?  

Yes that is why, I have key scramble on my compute, there is a green bar, that shows up on the top of your computer, and everytime you hit a key stroke, it will scramble the keys, that way no one can detect what keys, you are hitting it sage and it neat.

Well, first off, hiya :D.
Ok well, there is always the, 'previously visited sites' function in the favorites tab. which allows anyone on your computer to see what you have been doing for up to the past week. and, for recording key strokes, that is possible, 'Keylogger' A Completely LEGAL program, is usually set by supervisors at work, or parents at home, to see what their kids talk about, on myspace, facebook, chatrooms, anything you type is saved and recorded. Now if you share this computer, and you are underage, your parents are watching you most likely.
If your uncomfortable allowing people to see what sites you visit, you can go to
'tools' click 'internet options' then 'delete browsing history' and finally. 'delete all'
give it less than 20 seconds
and. poof. gone :)
As for keylogger.
Either another user of the computer set it up for you.
Or, you have been illegally interfered, as in, another person from another computer tricked you into downloading keyloggers and is watching your every move, id be careful paying bills or checking personal emails

Always have software such as Adaware to sniff out those malware and keystroke recorder.

Yeah.. I have used in my one application.. it was for backend entries. but if you use it for stealing usernames and passwords then it's called keyloggers. which can be used in virus.

guess there is key-loggers in your system.. while typing your password use onscreen keyboard,its an virtual keyboard, just type osk in run and hit enter. it might help to against some key-loggers but there are smarter key-loggers that can even detect virtual keyboards..