Comment by input_sh
How's it free if it's not available in the Home edition of Windows?
In fact it's pretty much the only difference between Home and Professional editions of Windows these days, so I'd price it as the difference between the two (about $60).
IIRC the Home editions of Windows now do have drive encryption at least if signed into with a Microsoft account, but they have almost no features for managing that encryption beyond turning it off or getting the recovery key from the MS account.
At the time I was talking about, Bitlocker drive encryption on Windows 7 required either Enterprise or Ultimate, and for a 2-5 person office with no domain and a couple laptops they wanted encrypted outside the office Truecrypt was a perfectly viable option.