I have a 300 Gb HDD.
200 Gb for Windows7 and 100 Gb for Backtrack5. Both OS were allready installed.
The Partitions for Backtrack5 were automatically created during the installation process (not manually).

Now I like to encrypt my whole HDD. I found a toturial , the problem is that i've allready installed everything. If I format the Backtack-Partition again, I would have problems with the Mbr.
Also I have a bad feeling when I try to encrypt both OS with truecrypt separately, because I think there will be problems with grub and truecrypt and truecrypt itself.

What should I do now?