itunes problem with syncing into my iphone?

[Ken S]

i have an iPhone that has apps and music stored in it.and recently all my musics and apps in my other computer got deleted because the computer had a virus or something. and now im just afraid that if i try plugging it in the computer that all my stuff in the iPhone will get deleted. some of the apps are free so i use my own account for that but the others that are paid are my cousins help me!! how to make sure that i don't allow it to delete my music and apps and so that i can put more music into it!!