These are the steps I would take using OS X and iTunes version 9.02. If you are using Windows than the menu names might differ a little but you should be able to figure out how to get around based on these steps:
-Before plugging into your friend’s computer be sure to open up the iTunes Preferences of that computer. Now at the top there should be eight menus. The one to click would be the second-last one. Our OS X Macbook runs in Canadian French and says ’‘Appareils’’ so in English the menu is probably called ’‘Devices’’.
-Make sure the first check box under that menu is left unchecked and should say something like ’‘Prevent automatic synchronization of iPod and iPhone.’’ Click OK.
Now you can plug your iPhone into your friend’s computer.
-Next click on your iPhone device in the left column of iTunes and make sure that when a new set of menus pops up in iTunes you are on the left-most menu. Then you should see a category called ’‘Options’’.
Should be self-explanatory from there.
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