Thank you for pointing out Truecrypt; I will check it out. However, doesn't that seem like overkill for hundreds of gigabytes photos?
Once the TrueCrypt "disk" is created, its use is just like any other disk on the system. Essentially, set it and forget it.
My personal files are on a 10 GB TrueCrypt disk (about 60% used), replicated on a laptop and a desktop (different locations), on a USB portable disk (for synchronization of the two machines), and also on a third disk in a third location----all to protect my information from theft and from loss.
I would think a 500 GB "disk" (for a photo archive you would like to keep private, say) would work equally well, but I have not tried it.
By the way, I initially explored Windows tools, but my experience was that the more secure they are (Encrypted File System), the more careful one needs to be to not get locked out and with synchronizing across machines.
Most important to me. though, I am grateful to have found in TrueCrypt a secure, all-platform (Windows, Mac, and Linux) tool, based on vetted public domain code. I just hope it remains so problem free!