MPC Sound Quality... or lack thereof, Sounds lousy in MPC, wasn't before, which codec is it? Options

[Fritters]

I recently downloaded several codecs, not sure which, and installed them. I noticed later that a lot of my favorite mp3s had VERY crappy sound quality in media player classic. I called Dell, they were precious little help (let's wipe your hard drive!!). The mp3s sound okay in Windows Media Player and winamp. The main problem is a lot of distortion and flattening out, if you know what I mean. I've tried uninstalling and reinstalling divx. I've tried un- and re-installing media player classic. I've tried getting new versions of the mp3s in case they got corrupted somehow. I've run codecfixer, codectweaktool, sherlock, and big fix, dxman and codecinstaller. I've also tried mp3checker and mp3repair in case the files had a problem and NOTHING. Granted, a lot of the programs listed above I'm not sure I even know what I'm looking for, I'm a complete n00b at this. I'd uninstall what I installed before the day I installed several items, but I'm not seeing any uninstallers lying about and don't remember what I put in.

I don't know if this is related, but at SOME point, I can't guarantee if it was before or after I installed the codecs, iTunes stopped working. I couldn't start it at all. I tried uninstalling and reinstalling every apple product on my hard drive, including quicktime and bonjour, and nothing would let me reinstall iTunes without it crashing on startup. This MAY be unrelated, though.

I have the latest version of my audio driver, I have nothing showing up on virus scans or bot scans. I'd like to uninstall any unnecessary audio codecs, but I have no idea even what those are. Any suggestions on what to do, where to start, what I've missed? Please keep in mind I'm a noob, but ANY help is SOOO appreciated! I'm going nuts here trying things...

Big Hugs in advance