At the end of last month, the TrueCrypt web site announced a warning that "TrueCrypt is not secure as it may contain unfixed security issues" and that development was ended in May 2014 after Microsoft terminated support for Windows XP.
There has been much speculation about the reason for its sudden disappearance:
And now, in the wake of an attempt to keep it alive (in violation of the license terms), a survey of 100 IT pros showed that TrueCrypt was being widely used (tied with BitLocker as disk encryption method).
If you've been using TrueCrypt, it might be time to switch over to BitLocker. And if you can't do that because you're still using XP, it's way past time to fix that.