How to hide a folder on Windows

This rather old method (and not tested for Windows 8) is a fast and effective way to hide a folder under Windows.

You can then "protect" a file for reasons that are unique to you and here's how:

Windows uses unique global identifiers for each software component ( GUID for Global Unique Identifier ), also known as Class Id ( CLSID ). 
These series of numbers and letters are in the Windows registry.

To access it just type regedit.exe in the search bar of the start menu under Windows 7 and Vista or click Start -> Run and write regedit.exe under Windows XP.

Then open the key HKEY_CLASSES_ROOTCLSID

There are for example the famous CLSID of the Trash (Recycle Bin): {} 645FF040-5081-101B-9F08-00AA002F954E .

How to proceed ?

Windows interprets the names of folders containing CLSIDs, so you can transform a folder into a Recycle Bin by calling it:

<Name>. {645FF040-5081-101B-9F08-00AA002F954E}

<name> can be any authorized folder name. Do not forget the point and copy the CLSID well.

The folder is transformed into a Recycle Bin, and a double-click on it displays the contents of the Recycle Bin !

To go back:
Rename the folder to any name allowed for folders.

You can now hide files in the original folder and rename it with the CLSID and the average user will no longer be able to see the contents of your folder.

This trick is not infallible because a wise person can of course find the original file by renaming it. 
However, this is an effective technique in some cases when you have something to hide, without having to resort to specialized software for example.

(By the way, if you are interested in professionally encrypting folders and files, I recommend the excellent TrueCrypt ).

You can also hide the newly created folder by right-clicking it and checking the Hidden box . It will not be visible at all if you have chosen not to display hidden folders and files:

Tools -> Folder Options -> View tab -> check Show hidden files and folders in XP

Organize -> Folder and Search Options -> View tab -> check Show hidden files and folders in Windows 7

List of the main CLSID

 CLSID MEANING
 {d20ea4e1-3957-11d2-a40b-0c5020524153} Administrative Tools
 {21ec2o2o-3aea-1o69-a2dd-08002b30309d} Control Panel
 {d20ea4e1-3957-11d2-a40b-0c5020524152} Fonts
 {00020d75-0000-0000-c000-000000000046} Inbox
 {20d04fe0-3aea-1069-a2d8-08002b30309d} Computer
 {450d8fba-ad25-11d0-98a8-0800361b1103} My Documents
 {208d2c60-3aea-1069-a2d7-08002b30309d} Networks
 {7007acc7-3202-11d1-aad2-00805fc1270e} Network Connections
 {2227a280-3aea-1069-a2de-08002b30309d} Printers
 {7be9d83c-a729-4d97-b5a7-1b7313c39e0a} Programs
 {645ff040-5081-101b-9f08-00aa002f954e} Recycle Bin
 {e211b736-43fd-11d1-9efb-0000f8757fcd} Scanners and cameras
 {d6277990-4c6a-11cf-8d87-00aa0060f5bf} Scheduled Tasks