It will not be the programs that occupy drive space. It's the data.
You have a couple of choices. You have go through an start deleting old, unused data or start backing it up to external media such as CD's, DVD's, or external hard drives.
I am assuming you are talking about a laptop. If so, you can clone your hard drive onto a larger one, but that's a more complicated affair. And all it will do is postpone the problem.
If a desktop, add another hard drive.