I use MiniTool Partition Wizard Home Edition 7.0 it's safe and doesn't lose files... but program it to do a few tasks (2-3) at a time just to be on the safe side. This doesn't mean it's unsafe to use but al the opposite... if you don't complicate the tasks.
It's a good idea to defragment the hard drive before you partition it. Then begin by separating the System partition first.. then partition the rest of unallocated disk space into the number of partitions you want without affecting the Operating System. For example: if your HD is 500GB... and divide it into a 100GB partition for the system, leaving a 400GB unallocated disk space, then you can divide that space into more partitions without affecting the System partition... this would affect the System only once and you can create more partitions on the unallocated disk space without affecting it