HideIt!
HideIt! is your personal data key. With its help, you can easily and reliably hide any files on your home or work PC from outsiders, and unauthorized users. Nobody except you can get access to your hidden folders and files. No one will ever know that you made some of your files invisible to... The file you choose for hiding your data will also not be modified, its size remains the same as it was before hiding your data. ... This space is a private "hiding place" where you can store private data that only you know about.
http://www.guard-software.com/products/hideit/hideit_setup.zip - 708Kb - Download - Screenshot

Anti Boss Key - Hide windows quickly!
MindGems Inc. AntiBossKey allows you to instantly hide and restore the applications ( windows) on your screen in order to prevent uninvited persons from seeing them and to protect your privacy. There are not any adware, spy ware, banners or pop ups included in this package!
http://www.mindgems.com/software/abkinst.exe - 725Kb - Download - Screenshot

Magic Window Hider
Hide/Unhide any application/window with ease. Ever wanted to hide windows you did not want you boss/parents to see while u r working(or playing!!! ),magic windows let's u hide/unhide windows with ease. Also hides itself and displays the tilte of the hidden windows by pressing F7. ... Instructions: Press F7 to view the window's text Press F9 to hide any window (The mouse pointer should be above the window) Press F10 to unhide all windows Press F11 to hide me Press F12 to unhide me Click on the Start Hide button to begin hiding windows!!!!
http://www.pe.ws/Magic-Window-Hider.exe - 1Mb - Download - Screenshot

ATS Warning! The Boss!
Do you need to hide windows or complete applications from the sight of others? To surf through the internet without anyone seeing the contents of the sites you have access to? To keep a conversation using a messenger or enter the number of your bank account with total privacy? ... Moreover, you will be able to hide icons in the systray and silence your PC when you want even if you are not hiding windows. ... Control the visibility by hotkeys that will give you total control of each window, hiding and showing them according to your needs.
http://www.apituan.com/dcs/Wtb160.msi - 2Mb - Download - Screenshot

Hide Window Hotkey
Hide Window Hotkey is a utility which allows you to hide the windows, and programs which are running on your screen. It will instantly hide or close all (or some) programs on your screen through Mouse Hotkey or Keyboard Hotkey in order to prevent uninvited persons from seeing them. ... By hiding windows you have the freedom to protect your privacy and hide sensitive information from praying eyes. ... You can set other options too, such as muting all sounds during hiding, specifying hotkeys etc. ... It can also protect the hidden windows with a password.
http://www.elongsoft.com/download/HWHSetup.exe - 883Kb - Download - Screenshot

Quick Hide Windows
Quick Hide Windows by CronoSoft is great for hiding program windows with a press of a hotkey combination. You easily bring them back with another combo. Hiding the taskbar and desktop icons is just awesome. Password protection allows you to lock QHW to prevent intruders from trying to show... You can even lock your computer with QHW instead of a weak, easily hackable screensaver password.
http://www.cronosoft.com/files/qhw.zip - 994Kb - Download - Screenshot

Hermetic Stego
Hermetic Stego is a steganography program which allows you to encrypt and hide a message (the contents of any computer file) in another file so that the addition of the message to the container file will not noticeably change the appearance of that file. ... Hermetic Stego allows two operations: (i) hiding a message file in single BMP image file or in a set of BMP images and (ii) extracting a message file from a single BMP image file or a set of them. ... This program allows hiding a file of any size in one or more BMP image files, with or without the use of a user-specified...
http://www.hermetic.ch/hst/hst_setup.zip - 3Mb - Download - Screenshot

Anti Boss Key Light Edition - Hide windows quickly. Hide your screen!
MindGems Inc. AntiBossKey - instantly hide windows (applications) in order to prevent uninvited persons from seeing them and to protect your privacy. There are not any adware, spy ware, banners or pop ups included in this package!
http://www.mindgems.com/software/abkle.exe - 705Kb - Download - Screenshot

Steganography
Steganography: an excellent method of embedding information on the contents of the file within another file! Make your secrets invisible in just 3 quick steps! Steganography enables you to use digital data hiding techniques (steganography) to hide files and messages within other files... This allows you to encrypt sensitive information, while at the same time hiding it in a file that will not look suspicious, so nobody even knows that there is any encrypted information. ... securekit. ... com .
http://www.securekit.com/sg.exe - 1Mb - Download - Screenshot

4t Tray Minimizer Free
4t Tray Minimizer lets you running applications minimized as System Tray icons, which helps in adjusting free space on your taskbar. To minimize any application to the task bar, simply left click the minimize button as usual or press keyboard shortcut. ... For example, if your mail client (MS Outlook) changes the icon on the new message arrival, its tray icon changes accordingly -Shows/Hides icons in the Alt+Tab dialog -Hides and Restores all opening application For your favorite application: -Customized keyboard shortcuts for quick launching and hiding your favorite application...
http://www.4t-niagara.com/4t-min.zip - 613Kb - Download - Screenshot