Lower PC’s memory usage: msconfig startup list

Hi! I have a few items to ask about what to uncheck on my msconfig startup list. I want to lower my pc's memory usage because it uses above 1.5gb.
Here are some of the items:
Realtek Audio Manager
Google Update
Java (TM) Platform SE Auto Updater 2 0
Please also tell me what will happen if I will uncheck them. Thank you!
