How to sync my iphone 4 with a different PC?

I have an Iphone 4 and I want to update it to ios 7. But I can't use the PC I've synced my iphone. I've installed itunes to another computer. But I don't know how to sync without deleting my apps and photos. What to do?

Thats why i hate apple. They won't let you do it or all your data will gone

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