As I promised yesterday in another thread, I wrote a utility that extracts white games only, black games only or all games from a pgn file by player(s) whose name begins with a user supplied string. Besides the output pgn file (the input pgn file is unaffected) there is a manifest file that gives the FULL name of the players for each game extracted.
The link is on Jim Ablett's excellent site:
http://homepages.tesco.net/henry.ablett/jims.html
The program is called "Extract". It is easy to use.
example of usage in a command window:
extract alpha.pgn Karp black
this will extract all games in alpha.pgn played as black by player(s) whose name begins with "Karp". An accompanying manifest file helps you decide which games to delete in the event that you get more games than you expected. For example you might get games from Alexander Karpov and/or Aleksandr Karpatchev as well as Anatoly Karpov. A readme.txt is included.
If you combine this tool with another one of mine on Jim's site, you can then separate the black games into files for wins, losses and draws.