and works with my daul boot 64 & 32 bit system perfectly,what I did was putting the 64 bit image in the 32 bit drive, and 32 bit image in the 64 bit drive. The external drive is an excellent idea if you can afford it and prefer extra space.
My way is Acronis but you make your choice. I just use it for creating Images so it will work on all if you have a External Drive to copy Images to. Or create Image to other Partition, then copy to Ex drive.
PS I created a Rescue Boot CD with Acronis so I can get to load a Image even if PC does not boot because of windows or Virus