There is an alternative, simple boot/install method to the official one posted on the "How To" as follows:
1. install WIN 7 for the first (it will create its BCD bootloader)
2. leave or (free up by shrinking etc) a large enough unallocated space on the drive (continuous free space!), very minimum 10GB but if you will want to install further apps than allow a much larger one to BT partition.
3. boot the PC from a BT4 R2 DVD to start installation
4. choose any of the offered load options (Graphical or command mode etc)
5. BT4 partitioner will load and there you have to choose the "Guided, use the largest free space" option for installing BT4
6. VERY IMPORTANT (if you do not want the orginal MBR/Win bootloader being touched/modfied by BT4/GRUB):
Before you would click on the last "OK" there is an "advanced options" -or named something like this- button on the screen where you HAVE to select "install bootloader" not onto the main partition (WIN7 neither its 100MB system reserved partition) BUT choose the free partion for this to where you install BT4 (not its other swap file partition which has been automatically created by now)
7. After you have installed BT4 fully (run install.sh from BT4 desktop, standard way, as described on the "How To" main site), you need to reboot and Win7 will boot now. Now install EasyBCD from the web and using this app add a new entry to the Win multiboot section (named as you wish ie BackTrack or so), click SAVE, than OK.
Reboot and you will be offered the multiboot choice.
Following this procedure, the GRUB bootloader will not touch the original MBR or the WIN BCD loader, so that it might cause you less hassle if you have any partition/MBR related issues on Win7 (recovery, MBR damage, partitioning etc). I use this dual boot system and it has no any problem.
I did not try on this dual boot setup yet, but I am confident that it allows you to use full disc encryption under Win7 like the open source TrueCrypt or PGP WDE, Bitlocker etc). of course ONLY on the Win partitions not incuding the BT4 partitions! If you need BT4 partitons may be FDE encrypted under from BT4, so not from under Win7.