In order to actually activate the hidden operating system features, you’ll need to make sure that your hard drive is partitioned in a very particular way: You’ll need two partitions on your drive, and the first partition has to have your Windows install on it. The second partition needs to be bigger than the first, and if you’re using NTFS as your file system, it will need to be at least 2.1 times as big as the first partition. You can re-partition your current drive, but your best bet will be a clean installation. (As with skinning a cat, there are many ways to partition a hard drive. Windows 7 and Vista have built in partitioning tools [open Computer Management, then go to Storage -> Disk Management in the sidebar], or you could check out our guide to dual booting Windows 7 as a solid resource to get started with a partitioned system.)
This will pop up a wizard that will help create the new TrueCrypt volume to house the hidden operating system, which will live inside of a hidden volume on the secondary partition. Your best bet the first time around is to just choose Single-boot—leave the multi-boot for the advanced class.
The Volume Encryption options page is important for one primary reason, namely that you need to choose the same encryption method across the board while you’re running through this process. You’ll be prompted a number of times to choose the encryption, and you need to always choose the same one or else you can’t boot or access your data—also, the default setting of AES encryption is much, much faster than any other option.
You’ll be prompted to choose the outer volume password, which will house a set of decoy files to make people believe that your TrueCrypt volume on the second partition contains nothing more than a bunch of files you don’t want people to see—except the files you put on the outer volume aren’t actually meant to be a secret. Make sure you don’t lose this password.
Next you’ll be asked whether or not you want to store large files on the TrueCrypt outer volume. This choice is up to you, but there’s probably no reason to choose yes here.
Once the outer volume is created, you’ll be prompted to put some files there to make sure it looks like a real drive in case you’re asked to open your TrueCrypt volume.
Next you’ll be asked to create a password for the hidden volume, which will contain the hidden operating system. It’s crucially important that you choose a different password here, make sure it’s difficult, and make sure that you don’t forget it.
At this step you’ll be asked to reboot your PC and re-enter the password for the hidden operating system. Your new hidden OS will be copied from your primary operating system and encrypted into your newly created hidden volume. Readers should note that this process can take an extremely long time—you’ll want to let this run overnight.
Once the hidden operating system has been created, you’ll be able to boot directly into it by using the hidden password, and then you’ll be prompted to wipe the original system off the first partition. This process can also take a few hours, so go do something else while it’s running.
At this point you’ll have a hidden operating system, accessible by using the hidden password. The outer volume password won’t do anything, and hitting Esc at the TrueCrypt boot loader screen will take you to a page saying there’s no bootable operating system.
When you boot into your hidden operating system, you’ll notice that you still see two drives, and the C: drive appears to be the same as it was before, but it’s actually living in the encrypted volume, which is on the second drive that you aren’t able to access. Whatever you do, leave that second drive alone-don’t try to use partition tools to reformat or anything else.