First go to Taldren\StarfleetCommandII\MetaAssets\Singleplayer\character.gf. Open this file with a text editor such as WordPad. Then look at the top of the file. You will find a line that says "StartingPrestige=50". Change the number from 50 to whatever you want, then save the file and start the game. Now you will see that you have whatever you put in as your starting prestige.