I use pre-boot authentication. Can I configure the TrueCrypt Boot Loader to display only a fake error message?
Yes (as of TrueCrypt 6.1). To do so, boot the encrypted system, start TrueCrypt, select Settings > System Encryption, enable the option ‘Do not show any texts in the pre-boot authentication screen’ and enter the fake error message in the corresponding field (for example, the “Missing operating system” message, which is normally displayed by the Windows boot loader if it finds no Windows boot partition). It is, however, important to note that if the adversary can analyze the content of the hard drive, he can still find out that it contains the TrueCrypt boot loader.