1 step:
Fully unninstall BF2 using RevoUnninstaller or Iobit unninstaller.
2 step:
Log in onto battlelog, download their launcher and install the game from there.
3 step:
Check your firewall settings, make sure BF2 and battlelog launcher are allowed on private and public connections.
4 step:
Don't ever use those Baidu, GameBooster, etc software. Its just placebo effect and they can do more harm than good.