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:
If the volume is partition-hosted (applies also to USB flash drives), in addition to the steps 1-3, do the following:
By Andrew Y. (@andryou) - no affiliation with TrueCrypt - fair use - site for non-monetary, reference purposes only