New features:
- Full compatibility with 32-bit and 64-bit Windows Vista:
- Support for User Account Control (UAC).
- All .sys and .exe files of TrueCrypt are now digitally signed with the digital certificate of the TrueCrypt Foundation, which was issued by the certification authority GlobalSign.
- When moving the mouse on a single-CPU computer while reading or writing data to a TrueCrypt volume, the mouse pointer stopped moving for a second every few seconds. This will no longer occur. (Windows Vista issue)
- Other minor compatibility-related changes.
- TrueCrypt volume is automatically dismounted if its host device is inadvertently removed.
Important: You should always dismount the volume in TrueCrypt and then use the "Safely Remove Hardware" function (built in Windows) before you physically remove the host device (e.g. a USB flash drive).
- Support for devices and file systems that use a sector size other than 512 bytes (e.g., new hard drives, USB flash drives, DVD-RAM, MP3 players, etc.)
- Support for devices with a GPT partition table (GUID partitions). (Windows Vista/2003/XP)
- After a partition is successfully encrypted, the drive letter assigned to it (if any) is automatically removed. (Windows)
- Volume name (label) is displayed in device/partition selector. (Windows)
- New hotkey: 'Wipe Cache'. (Windows)
- New command line switch '/q background' for launching the TrueCrypt Background Task. (Windows)

Improvements:
- Portions of the TrueCrypt device driver redesigned.
- Maximum allowed size of FAT32 volumes increased to 2 TB (note that NTFS volumes can be larger than 2 TB).
- Traveller Disk Setup improved. (Windows)
- Volumes hosted on read-only media will always be mounted in read-only mode. (Windows)
- Improved support for big-endian platforms.
- Other minor improvements (Windows and Linux)

Bug fixes:
- The built-in FAT format facility now functions correctly on big-endian platforms.
- Improved handling of partitions and devices during volume creation. (Windows)
- Improved handling of low-memory conditions. (Windows)
- Fixed bug that rarely caused system errors when dismounting all volumes. (Windows)
- Tray icon is recreated when Windows Explorer is restarted (e.g. after a system crash).
- Other minor bug fixes (Windows and Linux)

Security improvements:
- Improved security of set-euid mode of execution. Volume can be dismounted only by the user who mounted it or by an administrator (root). (Linux)

Removed features:
- It is no longer possible to create new volumes encrypted with 64-bit-block encryption algorithms (Blowfish, CAST-128, and Triple DES). 64-bit block ciphers are being phased out. It is still possible to mount such volumes using this version of TrueCrypt. However, it will not be possible to mount such volumes using TrueCrypt 5.0 and later versions (this applies also to volumes encrypted with AES-Blowfish and AES-Blowfish-Serpent, which have been in the process of being phased out since TrueCrypt 4.1). If you have such a volume, we recommend that you create a new TrueCrypt volume encrypted with a 128-bit-block encryption algorithm (e.g., AES, Serpent, Twofish, etc.) and that you move files from the old volume to the new one.