OS 10.5 - Hard drive space

Hi, I need some help understanding some basic of osx 10.5 installing files.
I have got a macbook with only 80 gb of HD. I have almost 70 gb used.
I have check the sizes of the different places in the hard drive, pics, movies, doc, applications, etc, and adds up to about 40 gb. Then if I check my own profile within the hard drive adds up the another 30 gb. The files that are under my profile are the same that in the HD under movies, pics, documents. I need to know if I could delete the files under my profile to make some more space.

thanks in advance.

K