what should not be deleted from sd card

[kirbysawhoor]

My first evo got weird so I just got a replacement, now the new one is doing the same thing. But I'm using the same sd card. So maybe it's the SD card and wondering if there's anything I shouldn't delete besides the obvious like pictures

 

[novarider]

What is it doing?

 

[kirbysawhoor]

password lock screen appears randomly, mostly when i hit home button or close an app and the volume level doesnt affect text message notification, no matter what level its at except for silent it plays loud as it can.