I have a 500GB external drive that I purchased when my primary machine was a PC. I've only filled about half of its capacity and need some external storage space for my MBP.

Is there a way to partition the remaining 250 GB to allow for data transfer from Mac O/S?

I know that there are "long" work arounds for this issue...i.e. transfering data via PC to a new HDD and then reformatting from scratch. However, I am trying to avoid buying a new HDD and/or losing the data is currently stored on my HDD.