I have an old iPhone 3GS that has been sitting in the lost and found in my business for about 2 years. I decided to start tinkering to see if it works. I was able to power it up, but it told me it needed to be formatted. I plugged it into iTunes and now it seems ready to go. The only problem is it does not have a SIM card and won't let me past the initial setup screen without it. Is there a way to figure out which carrier it is locked to so I can get a SIM card? If I plug in a random SIM card from a different carrier will it at least let me into the phone? I'd like to do something with it, sell it, donate it etc. It still appears to work fine, so it should go to someone who will use it. Thanks in advance for your input.