Reinstall 'Game Data' Folders Without Redownloading
Ok.. This one is only for the people that can make npdrm package files..
If you don't know how then I suggest a quick google search and you will see and maybe find what you need.. (Sorry can not help you there)
For those that do it is quite simple.. I will assume that in everyone's curiosity they have probally copied 'dev_hdd0/games' to their PC via FTP.. This is where you'll find your game data (updates), PSN Games and any games installed to the HDD via BD (checking the .SFO file of a particular folder will tell you what type it is).
Select the update you want to put back on your PS3
Make your package config file.. Remember that for 'Content_Type' you must use 'GameData' not 'GameExec'.. Something ike this..