Na FAQ do TrueCrypt :
Can I encrypt a partition/drive without losing the data currently stored on it?
Yes, but the following conditions must be met:
If you want to encrypt an entire system drive (which may contain multiple partitions) or a system partition (in other words, if you want to encrypt a drive or partition where Windows is installed), you can do so provided that you use TrueCrypt 5.0 or later and that you use Windows XP or a later version of Windows (such as Windows Vista) (select 'System' > 'Encrypt System Partition/Drive' and then follow the instructions in the wizard).
If you want to encrypt a non-system partition in place, you can do so provided that it contains an NTFS filesystem, that you use TrueCrypt 6.1 or later, and that you use Windows Vista or a later version of Windows (for example, Windows 7) (click 'Create Volume' > 'Encrypt a non-system partition' > 'Standard volume' > 'Select Device' > 'Encrypt partition in place' and then follow the instructions in the wizard).
As etapas para remover a criptografia são descritas aqui :
Please note that TrueCrypt can in-place decrypt only system partitions and system drives (select System > Permanently Decrypt System Partition/Drive). If you need to remove encryption (e.g., if you no longer need encryption) from a non-system volume, please follow these steps:
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