Bitlocker in bootcamp Windows 7 on a MacBook Air (late 2010)

The MacBook Air (well at least the 11", late 2010 model) does not have a "TPM" chip, and you'll get an error if you try an enable Bitlocker on the drive. There is a work-around to disable the TPM requirement, though you will need to have a USB key handy every time you boot.

The following information was copied from http://www.sevenforums.com/tutorials/4681-bitlocker-drive-encryption-windows-7-drive-turn-off-no-tpm.html

To disable the TPM requirement:

1. Start the Group Policy Editor
2. Go to Computer Configuration, Administrative Templates, Windows Components, BitLocker Drive Encryption, and Operating System Drives
3. Edit the Require additional authentification at startup option
4. Select the Enable option
5. Run gpupdate.exe /force

Now you can enable Bitlocker.

UNFORTUNATELY, you then hit a snag with rEFIt not allowing you to boot off the USB key after Windows is installed, and the Bitlocker process requiring you to boot from the USB key to decrypt the drive. So, this process is pointless until rEFIt fixes that bug.