There are programs called keyloggers that record every keystroke and opened program in your computer. You can buy them from the web or your local computer store. Some most keyloggers have an "invisible" option that hides any trace of the installed program. It creates a hidden folder that only the owner can open, usually with a password. Many people buy these programs to keep tabs on what their children are doing online or even to spy on their husbands or wives. (It says a lot about how dysfunctional a person's family is if that person has to resort to spying.)
Be aware that while it is perfectly legal to use the software on YOUR computer, it is illegal to install it on someone else's computer without their consent.