Not sure if this is the place to post this...
Ok...Trying to help anyone that can't figure out the pb+legacy stuff.
I couldn't get the drop down in pb update for cod4 either. The Instructions given through google seraches and forums are confusing. I simply put the legacy files on one half the screen....and the actual cod4 pb file on the other half the screen. I then deleted the idividual cod files, in the pb folder of cod4, one at a time. Then dragged and dropped the legacy file that matched into the pb file for cod4. After that there were files still remaining in the legacy files...so I dragged and dropped them in the cod4 pb file. Started the game and was able to sit idle for a long time without issue from punk buster. If this helps ...great.
My thoughts about the whole thing is this: Why cant punk buster leave cod4 in the drop down? When players need to install pb using pb update... they would only recieve the files that were last updated before evenbalance stopped updating. That is the simplest thing in my eyes view. However there also may be other reasons for Evenbalance not having cod in ther at all. This may be because EA approached Evenbalance to have P.B. in BF4? Maybe EA said we will use Punk Buster...But you have to remove anything cod related...I Don't know...just a theory. Sort of a way to garuntee cod gets the least amount of attention? Who Knows. Spelling errors are a given...read through them as if they were the correct spelling. You should do fine.