Changing lock screen, pen pull and other system sounds?

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http://forum.xda-developers.com – I'm a nerd. I already have my notification sound being "incoming transmition" as said by the compiter from star trek tng and my ring tone being the opening credits. I want to edit system sounds to improve on this nerdyness. I remember changing the pen sound once but for the life of me I can't remember where. Any help would be appreciated. Sent from my SPH-L900 using xda app-developers app (HowTos)