Well... (don't worry, no essay this time :) )
There are certain things you can do to clean up songs, remove hiss, clicking (usually caused by clipping) and other things like that. It requires a little messing around with the song to do, and a little time to learn what each function does, but it is possible.
If you're wanting to experiment with things like that, I recommend the Audacity audio program. Its free, and has some basic filter abilities to it if memory serves.
As far as the volume being the same all around, that would be referred to as Normalizing or Audio leveling. However the problem with that (normalizing more so than audio leveling) is that it removes all the dynamics of the music (panning, cresendo (i know i mis-spelled it but its 2:30am) decresendo (again spelling) etc.) so the song has some of its subtleties taken away.
WMP has a audio leveling ability if memory serves, I'll need to find it and I'll post back when I do.

Okay so it was kinda long, but not as bad as I normally am :)

lol, alright... just remember you said I could :)
Luckily for me, I'm an audio major and also tech certified so this kinda stuff goes hand in hand. Another reason why I don't mind helping people here, cause it keeps me from getting rusty. But anywho..

Audacity can be downloaded at http://audacity.sourceforge.net/
Its a freeware program (free) and doesn't have any adware or anything like that. (I always make sure before I link or mention Freeware programs (scanned 5 times by different programs))

Once you have downloaded it I recommend just poking around on it (Don't save anything as it will do whats referred to as a Destructive overwrite) meaning you can't undo it if you save. I recommend opening your music file and immediately renaming it something different i.e Mysong renamed to Mysong2 until you get the hang of it.

I'll make a picture walkthrough similar to my AVC walkthrough with some basic functions, and probably a basic tutorial on how to repair a track. I'll only go into the lite aspect of audio restoration cause if I went into detail, well it would turn into a 6 week class lol.
I should have the walkthrough created within the next couple of days or so

Just to update you and anyone else who is hoping to use the walkthrough.
After 2 days of almost straight sleeping (first sleep I've had in almost 2 weeks (YAY energy drinks)) I am reved and working on the Audacity Walkthrough. I talked it over with Brandon and Matt and we've decided the best way for me to do the walkthrough will be Video. That way it can be paused and rewound and also serves as a better audio/video aid then just pictures.
Sooo.... I'm working on that, I'll be making it into sections for not only ease of use for the user looking for something specific, but for streaming purposes.
So far here is what I either have done, or am working on (its all going to be released at once tho):

Intro: Your Workspace
How to Import a File:
What is that squiggly thing? (The wave read-out and what it is)
Tools and Their Functions:
Filters and Effects: Audio Restoration
Filters and Effects: Normalizing and Audio Leveling (How to not blow an ear drum)
Saving Changes: Passive and Destructive saving/editing


If there's anything that you Tgirl or anyone else browsing through would like me to touch on, please let me know (you don't have to know the prog, just a general "How or Could I do something like this?" will suffice. If its possible, to do, I can work that in there somewhere if Audacity has the ability. If not, I'm sure I can start something else on another prog that has that ability.