It's rather uncommon system upgrade suggestion but it can seriusly improve sytem security by completely stealth control of computer usage. Any "uninvited guests" operating from our PC will leave a trace on embedded logger. What's interesting logger can't be tracked by any software scanner as it's 100% hardware solution.
I've found some DIY project describing how to build hardware keyloger at home... http://www.keelog.com/diy.html
it's possible to make an embeddable module to be installed inside keyboard (click the keyboard photo below for animated gif).
There is also the commercial aspect of KeeLog company activity... their offer includes already made professional USB and Ps/2 keyloggers... but unfortunately you have to pay for it.