TrueCrypt 7.1a

Excellent Encryption Software and it's free..

Download - TrueCrypt 7.1a

I really like this for the OS drive eg encrypting the hidden partition (100MB or 300MB on Win 8), C and any other partitions on that disk. But using it for encrypting other partitions that are on a different drive/volume is horrible.

I wanted to encrypt my D drive, C is 2x 120GB Corsair Force 3 in RAID0, and D is a 1TB Partition on my 2x 1TB WD Black drives in RAID0 so I encrypt D and once done (7 hours later) it tells me I can't assign the letter D to it, so when I open Explorer there's a D drive with no info and then K (for example) that is my actual D drive, all my Pictures, Docs and Favorites are linked to D and to be honest I want my drive letter in order and not all over the place.
It seems like a big mess so I decrypted it and went back to use BitLocker on D.

On my Laptop, the system partition, C and D are all on the same hard drive so that's great as it's covered when you use the "Encrypt System Drive" option.

Still it's an excellent piece of software and well worth looking into if you are looking for Encryption software.

It took just 43 mins to encrypt the 2x 120GB Corsair Force 3's RAID0 array, and the laptop took 8 hours to do the 500GB (460GB Formatted) 5400RPM Seagate drive, thankfully it does this in the background so you can keep using your PC.You can also pause and defer the encryption process.

Oh, I just found a limitation - unable to use UEFI and GPT so you can't encrypt the system drive/partition :(
Only people using MBR Disks can encrypt the system drive/partition.