TrueCrypt is an open-source encryption software that enables you to create a virtual encrypted disk within a file and mount it as a virtual disk, that can be accessed via a drive letter. Any file that is stored on this virtual drive is automatically encrypted on-the-fly, and can only be accessed while the drive is mounted with the correct password or key. TrueCrypt supports a variety of encryption algorithms, including AES-256, Blowfish (448-bit key), CAST5, Serpent, Triple DES, and Twofish. Other features include support for FAT32 or NTFS formatting, hidden volumes, hotkeys for mounting/dismounting and more.
It is important that TrueCrypt is freeware.
GiliSoft Private Disk also enables you to create a virtual encrypted disk within a file and mount it as a virtual disk, that can be accessed via a drive letter. Any file that is stored on this virtual drive is automatically encrypted on-the-fly, and can only be accessed while the drive is mounted with the correct password.
GiliSoft Private Disk provides a more secure features that is it can hide the image file when you unmout the virtual disk. So nobody can delete or copy it from your hard disk.
GiliSoft Private Disk provides a more powerful function that is it can install the virtual disk onto USB device,and the operation is very easy for computer users.