TrueCrypt remains the choice when PC users create encrypted virtual disks or encrypt a single partition or any storage device, including USB flash drives. It is one of the smallest apps available for protecting your documents, which also comes for free and remains like that.
One advantage can be considered the possibility of encrypting Windows partitions. Thus, pre-boot authentication is included.
By using advanced pipelining technology and hardware acceleration techniques, you will feel no difference between how data got stored before and after encryption.