Can i make my iphone 4 into JUST a music player?

Wow that's crazy I've never heard of an iPad/iPhone/iPod Touch without an ios, no matter where it was purchased from. Sounds like it has been or someone has tried to jailbreak it and they F'd up, that is thee only other way there is no internal operating system. Are you connected to the internet, do you have the latest version of iTunes (iTunes 10.3) that is required for the iPhone 4. Have you tried resetting your iPhone, you know holding the Home button for 5 sec. continue holding the Home button and press & hold the Power buttons together got 15 sec. release the Home button and continue holding the Power button for an additional 30 sec. or until the apple icon reappears, this is how to reset any iPad/iPhone/iPod Touch. If this doesn't work you may need to take it to an Apple store, if the iPhone hasn't been or tried to be jailbroken, because when you tamper with the ios it voids the warranty. there they can give you more advise don't worry it's free to find out what's wrong with your device.