How To: Encrypt Your Entire Hard Drive The Easy Way Using TrueCrypt
5. Start With a Clean Slate by Scrubbing Your Old Data
If the disk you are encrypting is new, this step won’t be necessary. Essentially what TrueCrypt is allowing you to do here is to wipe any data that you have deleted previously, but might still be recoverable using third party tools. Because True Crypt will only encrypt your current or new files, everything done and deleted in the past will still in the clear.
You have several wipe options available to pick from and they range in both the amount of time needed, and effectiveness. The higher options also defiantly suffer from a high rate of diminishing returns. 3 pass setting is generally enough to defeat all but the most advanced and expensive governmental tools, while the 35 pass setting is insanely overkill and generally a waste of your time. Depending on the size of the drive, and the setting selected, this step can range from a few hours to several days. Once you're ready to continue click Next.
6. Run the Pretests & Get Ready to Encrypt
Next True Crypt is going to test your memory by restarting your computer, and giving you the opportunity to enter your master password for yourself.
If you fail to enter the password successfully (or have forgotten it) do not fear, your still safe at this stage. Following the reboot TrueCrypt will bring you back into Windows where you will be forced to reconfirm your master password. Since no encryption has been performed yet, this is simply a test to make sure you have your login information memorized. From this point forward, forgetting your master password will result in 100 per cent data loss (except the backups you made right?).
Now simply Click Encrypt to begin the process. You will still be able to use the OS while the encryption process is underway. The TrueCrypt driver keeps track of what data is, and is not encrypted, and operates completely transparently
Congratulations you're all done! If you ever run into any issues while booting, continue on to the troubleshooting section for a look at how to use the rescue CD.