From SuperUser:

I’ve done it but not exactly like in your link, because of some kind of problem (bug?) in Grub2 (tutorial is with grub “1″ but I’ve Grub2), specifically in this

title Windows Vista/Longhorn
rootnoverify (hd0,0) makeactive
chainloader (hd0,1)/truecrypt.mbr
boot

The problem is known and posted on many forums.

My solution was:

1. Encrypt Windows7 system partition using truecrypt, selecting Single boot and overwriting Grub2 loader with truecrypt loader
2. Boot Debian from Rescue CD and install grub2 bootloader NOT on MBR but on /dev/sda3 which is Debian / partition (so truecrypt loader was not overrided)

Now while booting truecrypt bootmenu is shown and if I’d access Win7 I’m entering password, but if I’d enter debian (via Grub2) I hit esc key and then truecrypt loader is searching all other partitions for boot loader and finding Grub2 which resides on /dev/sda3 and load system properly.

I think its the best way to do this for now (until sb find resolution for Grub2 to read /boot/truecrypt.mbr without errors).

The steps I used are as follows, in brief:
1) Installed Vista first (actually pre-installed on laptop)

2) Installed Ubuntu second using encrypted physical volume with LVM inside it and 2 partions / and swap inside the LVM(at this point, grub was in the MBR)

3) Ran full windows system encryption (not full disk encryption) through TrueCrypt and let it write its bootloader to the MBR. (obviously overwriting Grub in the MBR)

4) Booted with a live cd and copied the truecrypt bootloader from the MBR to a file in the /boot partition (sda2)
use these commands to do so:
dd if=/dev/sda of=/mnt/boot/truecrypt.mbr count=1 bs=512
dd if=/dev/sda of=/mnt/boot/truecrypt.backup count=8 bs=32256

5)Reinstalled grub to the MBR using these commands:
sudo grub
install (hd0,1)/grub/stage1 (hd0) (hd0,1)/grub/stage2 0×8000 p

6) Added a chainloader to the menu.lst Vista entry to point to the truecrypt bootloader within the /boot partition like so:

title Windows Vista/Longhorn
rootnoverify (hd0,0)
makeactive
chainloader (hd0,1)/truecrypt.mbr
boot

The only partition not encrypted in the /boot partition so far, which is fine. After grub loads, no matter which OS I choose, I enter a passphrase and that OS starts.

For more detailed instructions which I pulled from but which are for XP instead of Vista, use this link:

http://ubuntuforums.org/showthread.php?t=761530