Partition Encryptor

Does anyone know of a good partition encryptor for Windows? I know of an accountant who would like to encrypt her client's financial data. She's stuck with Windows until such time as a major company starts shipping yearly tax software for linux. Something like PGPdisk, only open source, would be best. -- Stirling Westrup | Use of the Internet by this poster sti@cam.org | is not to be construed as a tacit | endorsement of Western Technological | Civilization or its appurtenances.