Im putting all my cd on my harddrive player and when i listen to them some are loud and some are low sound levels, some have more bass then others is there a way to correct this?

You will have to normalize them, search for a free program to normalize mp3s.

you can use the nero built-in normalize filter after adding the files (as audio cd of course) select all of em right click and get into "properties" and goto "filters" there youll see a thing called "normalize" you might also wanna mess with the "equalizer" filter but its best to use that in seperate and not for all tracks you can make the bass lower as you want with it click "test selected filters" to preview the result , anyway in my opinion mp3gain is best for normalizing mp3s and its free get it @ http://mp3gain.sourceforge.net/ download the full version which includes the runtime files as you might need those too incase you dont alredy have em