Welcome to LQ....soon you will be asking Linux questions....
First, don't get upset by people who may have gotten up on the wrong side of bed and decide to dump on you because you are not as smart as they think they
You'll need to give us more details to get good help--eg size of the hard drive, how much is used, what OS, etc. Meanwhile, 3 tips:
1. If you're not sure what something does--and you have no way of re-installing it, then don't remove it.
2. If you don't have an install disk for the OS, be careful about changing anything.
3. If you have Windows, the best way to free up disk space might very well be to install Linux.