When a TrueCrypt volume is mounted, the operating system and third-party applications may write to unencrypted volumes (typically, to the unencrypted system volume) unencrypted information about the data stored in the TrueCrypt volume (e.g. filenames and locations of recently accessed files, databases created by file indexing tools, etc.), or the data itself in an unencrypted form (temporary files, etc.), or unencrypted information about the filesystem residing in the TrueCrypt volume. Note that Windows automatically records large amounts of potentially sensitive data, such as the names and locations of files you open, applications you run, etc.
In order to prevent data leaks, you must follow these steps (alternative steps may exist):
By Andrew Y. (@andryou) - no affiliation with TrueCrypt - fair use - site for non-monetary, reference purposes only