
TrueCrypt is a free open-source disk encryption software for Windows, Mac OS X, and Linux. It allows one to create virtual encrypted disks files (known as a “container”) within normal files and access them as if it were real disks.
By default, assuming you have TrueCrypt installed, when you you double-click on a TrueCrypt container, the TrueCrypt GUI is launched. Then you have to select a drive and click on Mount to get the password prompt.
This tutorial will show how you can directly mount a TrueCrypt container by simply double-clicking on it, skipping straight to the password prompt on Windows.
Steps:
1. Run Regedit (Winkey + R)
2. Navigate to: HKEY_CLASSES_ROOT\TrueCryptVolume\Shell\open\command

3. Double-click on (Default) to edit and append “Value data:” field with “/l x /a /q background /e” to the end of the path and save it. The final path will be:
"C:\Programs\TrueCrypt\TrueCrypt.exe" /v "%1" /l x /a /q background /e

That’s it! Now whenever you double-click on a TrueCrypt container (.tc) file, you will directly get a password prompt.

What does those parameters mean?
- /l x : Specifies the drive the volume is to be mounted onto. Replace “x” with any free drive letter your want.
- /a : Automatically mounts the volume.
- /q background: Mounts drive and minimize TrueCrypt to system tray. You can remove “background” to close TrueCrypt after mounting.
- /e : Open Windows Explorer window for the mounted volume.
Further parameters may be added, refer to the TrueCrypt command line usage guide.