Yes it is! But there is always a risk of data loss when partitioning so back-up your important files first.
I use Gparted for partitioning.
Using Gparted, you can shrink the partition to any size that's larger than the used portion of the partition. (you can shrink it from the front or the back, but it's better and faster to only adjust the marker from the back.)
The unallocated space can then be used to create new partitions. Remember that you can only have four primary partitions. If you want more than four, you have to make at least one of your primary partitions an extended partition first.
The most important part is that you cannot repartition a hard drive that is mounted. If you want to repartition the main hard drive, you have to boot from a live CD to do that. I use SystemRescueCD
because it already has all the tools included. Some people prefer to use Puppy or some other variant of Knoppix.
But always remember to backup important data first. Accidents do happen, even to the pros.
P.S: Are you sure you mean 5GB and not 500GB?