OK, Mr. G, and hiya again...
 
You will find many, OOOOH, MANY... pros & cons re: so-called Codec Packs... Best I know of for the vast majority of ppl out there is Cole2k 'Standard'... Current-latest version is 6.0.9 ----- 
It works. Never had anyone complain... Honest...
Thing is, remember... if you update WMP or install another player or something like RealPlayer, your Codecs will be changed... Life's a *****, eh ? 
Gosh, even big bad powerful me ain't allowed to type 'b i t c h' without the roBOT taking a slice ! What's the world coming too ?
Personally, I blame it all on Antipodeans !  
 
So, reinstall Cole2k, right ? 
Also, as you 'progress' with all of this stuff and you perhaps find something that you think is better, PLEASE be sure to let all of us know about it, right ? 
C U