mp3s: Fuzz, static etc. - "repair"/filtering app ?

[stargazer777]

Hi all -

I have a small collection (200 or so) mp3s which have ended up on an "archive" folder on my drive D:
Somewhere along the way, from ripping, to copying, etc. some of the tracks I play exhibit fuzziness in the bass range, static and so on.
At first I thought my headphones were at fault, but when I switched back to my 5.1 speaker system (including large bass-box speaker) many which had such problems then played fine, even with bass maxed out, etc.
Then I began to notice while this was the case with many of my mp3s, some of them refused to improve no matter what I did. I've come to realize more of the problem seems to fall on how it was recorded, copied, etc. rather than bad headphones (which I realize do contribute, in part to bad sound).
I am left with the question: Is there a GOOD app, perhaps open-source or shareware, which can "repair" fuzziness, static, etc. I am not a audiophile master wizard (or I wouldn't be asking for help), so if such apps exist, I need something reliable, that really works, and is easy to use.

Thanks in advance ...
- Dave G.
Virginia, USA