Define Safe?  I would never manipulate partitions unless I was ready to
do a full recovery... The process isn't bugged or error prone, but an
inconveniently timed power outage or hardware failure can do much more
damage than usual.

You failed to mention what version of Windows you use.  If it's Vista,
use Vista's partition resizing tools (Computer management GUI).  This
isn't a suggestion, ntfs tools (last I checked, might be updated now)
does not support changes Vista made, but Vista can resize partitions any
which way live without any need for defraging.