Everyone has some private information stored in files what they do not want to anybody to access. A good way to keep the private information private is to encrypt it. AES Crypt is a good encryption tool for Windows which lets you encrypt and decrypt any file on the fly. AES Crypt is open-source freeware and uses the industry standard AES cipher (also called Rijndael).
You can download the AES Crypt from http://www.aescrypt.com/download.html. The download is available for both 32-bit and 64-bit editions of Windows. Choose the one for your edition of Windows. It is recommended that you download the GUI edition and not the command line edition.
After you have installed AES Crypt, you can encrypt any file you want very easily. Just right-click over a file you want to encrypt and choose AES Encrypt from the popup menu as shown.
You will be asked to type in the password for encrypting the selected file. Type the password and type it again to verify that there was no typing mistake. Do not lose this password, because without it you will not be able to decrypt the encrypted file. Click on the OK button to start the encryption.
The selected file will be encrypted and an extension of .AES shall be appended to its original filename. The icon of the encrypted file changes to the icon of AES Crypt application. AES Crypt does not delete the original file. So after the encryption you would have both the original file and the encrypted file.
If later you want to decrypt this encrypted file, then just double-click on it. You can also right-click on it and select AES Decrypt.A new window would open up asking you to type the password. Type the password with which encrypted the original file and click the OK button. The decrypted file with the original extension will be extracted in the same folder as the encrypted file.
AES Crypt is a small, fast and useful tool for encrypting files. It does not have tons of options which make is very easy to use. AES Crypt comes with command line interface (CLI) version too, so you can use it in scripts too. Because it is open source software, there is no possibility of it having any backdoor either.