By default, TrueCrypt volumes are not displayed as backup destination, but changing a particular setting in program config files allows them to be displayed. The procedure is as follows.
\program\. Find the file
<Object ClassID="ComplexBackupWizard">and add the line
<Object ClassID="FileBackupWizard">and add the same line to it, as well.
Note: this workaround comes with side effects. The program will display other, non-TrueCrypt, locations that shouldn’t be used as backup destination, such as previously deleted partitions.
Note 2: backups can be secured without storing them on encrypted volumes. Instead, you can enable password protection. Password-protected backups are encrypted with a 256-bit key generated by using the password as a seed. It makes backups inaccessible without the original password, and ensures their security even on non-encrypted storage.