From Corouter Solutions:
Rijndael File Encryption Decryption Tool is a simple .NET tool which can encrypt, decrypt any type of file. It is based upon Rijndael cryptography algorithm.
Features of Rijndael File Encryption Decryption Tool:
No installation needed. Just double click and run the tool. Run from USB, DVD, HDD.
Smallest (only 700 KB in total).
Strong Key algorithm based on Rijndael algorithm.
Fastest Encryption and Decryption.