File transferring problems...

Hi, I just got my first mac about a week ago. Everything seems fairly straightforward except for the fact that I can't seem to make any changes to documents or folders which I've transferred from my old PC via a CD. I can delete files or reorganize them within folders but otherwise it's completely locked up. I can't even rename files. What's the reason for this and what do I need to do so I can save changes to my documents?

Oh yeah, my OS is 10.3.

Actually, I have another question:
How do I check the space left on my hard drive?

in any finder window, available hd space is shown on the bottom of the window. as far as these files, select them, then click File>Get Info, in the get info window, make sure "Locked" isnt checked, then in the ownership tab, make sure it says read and write, then click the arrow next to details, and make sure those under there say read and write.
then repair permissions.