hmmm nice, he might have installed a keylogger which is designed to check out what key presses are made during a session on the computer.
try hovering the mouse over each of the icons in the system tray (area on the very bottom right), it will tell you the name of each of the programs running there. Otherwise right click on blue bar at the bottom and select task manager, on the next screen select processes. try and note down all the files running and post it in here, can hopefully see if one is there.
These are all suggestions that wont involve key presses and so wont arouse suspicion, am sure there are other things too that will be suggested