While wandering along the Internet, I came across this great Disk Encryption tool called TrueCrypt. TrueCrypt is a free Open-Source Disk Encryption Tool that is very easy to use and offers advanced options to protect and secure your data while you save it on the hard disk.
TrueCrypt creates an Encrypted Disk (a volume would be appropriate) in a single file. This will will look and behave very much like any other file (like copy to a new location) and the integrity of the data stored into it is still very good. However, when you mount the volume, TrueCrypt mounts it as a NTFS/FAT32 drive with a drive letter making it look like a seperate disk or partition. Even when the volume is mounted, the files are still encrypted as they are in the memory.
TrueCrypt can work on Windows, Linux and MacOS.