I tried out the TrueCrypt whole disk encryption today and so far it looks pretty promising. You can download TrueCrypt 5 from http://www.truecrypt.org/downloads.php, which includes whole disk encryption (for Windows only). I have discovered one serious caveat though. Prior to encryption I had a partition on my drive that I was using as a TrueCrypt volume. Luckily I backed everything up from that volume because after the TrueCrypt whole disk encryption the volume would no longer mount. It was no longer assigned a drive letter and wouldn't mount if I selected it manually or attempted the 'auto-mount' option from within TrueCrypt. Beware that this whole disk encryption will likely destroy your TrueCrypt volumes! Be sure to move any important data out of those volumes before encrypting the whole disk.