iPhone sync to iTunes help!!!

Okay so I have an iPhone 3G. I recently just got a new laptop and downloaded iTunes on it. Before I got my new laptop, I had an old desktop with iTunes on it too. So I had my iPhone completely synced to my old desktop. BUT when I plug in my iPhone to my new laptop and you go to your iPhone's main page, it has check boxes at the bottom. There is a check box that says "manually manage music and videos" and when I check that off and then click "Apply", it says it NEEDS to erase all the songs on my iPhone. How do I manually manage music and videos for my iPhone on my iTunes without erasing/deleting all the songs?

I really need help! Thanks!

Wow are you serious? Is there anyone that can help me? lol I mean this is serious. LOL Please help guys! Thanks so much!

I guess it's because no one knows. Why not call the Apple Customer Service? I mean, they know the most.

I know a lot about the iPod Touch and stuff, but I know NOTHING about iTunes, syncing and all that. The only people that know everything are the Customer Service people. So give them a call, and they'll help.

Okay thanks and yeah I never remember to call Apple on their business times. LOL I usually remember to call at night like at 11:00 PM but they don't work at that time lol

If you are on us call to the apple customer care. It's toll free. Else you can copy the .isc file from your old computer