|"inexpensive (or free)"|
That the hard part about it. Companies that make this kind of software make it for corporate computers and it is expensive. If you are willing to go to Linux there is some free stuff out there.
Oh never mind they made one for Windows.
I also like,
but you have to run it on every machine and write a batch script to run the log out to a log file on one of your servers,
Unfortunately most of the free stuff requires you to know a little about scripting.