He is in your house, useing a computer that obviouly dose not belong to you. What dose it matter what they are hiding? I mean I do not get you need here. Are we talking about finding out if you bother or dad is surfing adult content? Or is this a wife husband thing?
Next question, do you have a non administrative login? If so how many rights do you have? What I mean is can you install anything? Can you delete? there is allways password capture.
http://www.keyghost.com/ http://www.keyghost.com/securekb.htm YOu probably want this
External KeyGhost Home Edition
(128,000 Keystroke Capacity)
$89
https://secure.keyghost.com/order/index.htm That is the fastest way to do this. Or you can spen a few months reading about windows XP vulnerabilities.
Certainly, if you are a brand new PC buyer or someone already using Windows 2000 you should take a serious look at Windows XP Pro. Similarly, anyone who plans on sharing their computer among multiple (especially inexperienced) users or handing control of their computer over to a house guest may find serious benefits in running WinXP Pro.
In WinXP, Microsoft has done a tremendous job at simplifying WinNT's complexities for the computer novice. While XP Pro has all the security/privacy features that came with Windows 2000 (and previous versions of NT) the intricacies and details are hidden behind simplified user interfaces. These simplified interfaces can be “turned off” on a user-by-user basis. So someone acting as the system administrator for a home PC could have full access to all the power of a Windows NT workstation, setting up security just the way the PC owner wants, while hiding the details for other power users as they slowly learn how to configure/maintain their machine.
This isn't to say that Microsoft has suddenly started releasing copies of Windows that are secure and private by default. WinXP still errs on the side of “convenience” rather than “security” when it is initially installed. WinXP Pro gives full and unlimited access to all user accounts and leaves all files viewable and accessible by default. You are left on your own to set up each account's password, privatize each account's files/preferences, and limit each account's access rights.
All this in spite of the fact that computer consultants, network and system administrators don't give even themselves full access rights to a PC when logged in using their normal, everyday account. The reason is simple... a program you are running will have a difficult time trashing the hard disk, crashing the PC, or screwing up the operating system to the point where the machine won't boot, if the program doesn't have the right to do anything more than what an ignorant, bumbling computer neophyte has the right to do. The same goes double for computer viruses.
http://www.newfangled.san-jose.ca.us/Hacking%20WinMe/WinXP%20and%20IE6/page4.html If he has one password he probably hasn't completely hardened the box.