If you're worried about surreptitious key-logging software recording your every keystroke, Keystroke Interference could be the handy security utility you've been looking for. Instead of trying to detect or disable keyloggers, it interferes with what they record as your keystrokes, inserting a random sequence of additional characters based on a proprietary algorithm.
Keystroke Interference has no interface, and is visible only as an icon in your system tray and Start menu. To get it to run at start-up, you must manually place it in your Startup folder. It also offers no configurable options. However, we didn't notice any drag on system resources. When testing the program against several keyloggers, it performed admirably by mucking up their logs of our keystrokes--just don't expect it to do much else.
If you're concerned that somebody's spying on you computer usage, Keystroke Interference is worth investing in if only to obfuscate your trail.