Portable HD Running Out of Space

For the past two months, my Speedy usage has surpassed 100 GB of traffic (upstream+downstream). This rarely happened in the past, as i only download TV series weekly, but now, i'm downloading Taiwan/Korean drama for long vacation after the semester ends.

So far, my 500 GB portable HD is running out of space due to massive download for these two months. I have downloaded more than 160 GB only for this month, so no wonder it is running out of space so quickly