You’re sort of right Jack Ponting but TrueCrypt’s publicly stated reason for discontinuing the project was that newer versions of Microsoft Windows have full support for encrypted disks and virtual disk images.
TrueCrypt is still very secure for most users and after it was discontinued there was an independent report commissioned which found that whilst TrueCrypt has some minor issues they’re not serious enough to merit stopping using the software. Just because it’s no longer developed doesn’t make it secure although you should look at moving to something still being updated.
There is a new project called VeraCrypt which is free and open source plus the developer has implemented the recommendations from the independent report to make the software more secure.
However if you’re using Windows I’d recommend sticking to BitLocker for full disk encryption simply because it is very tightly integrated into the operating system and doesn’t suffer from the problems that third-party encryption have. But you need Windows Professional, Education or Enterprise in order to use BitLocker so you’d have to pay for an upgrade if you’re a Home User.
The added benefit of BitLocker is that it’s fully supported by Microsoft and you know it’s going to work providing your system meets the minimum requirements. It offers protection against DMA attacks, supports UEFI, supports secure hibernation and locks down your system. Third-party full disk encryption can never be as comprehensive as that which is included as part of the OS.
If you’re using full disk encryption you still need file-level encryption if you want to share your files securely with people or upload them to a cloud service. This is what AxCrypt is for.