Restoring jailbroken iphone via sync to new computer

[sicdeath]

I read many articles about restoring a jailbroken iphone 4 4.2.1 baseband 03.10.01 to factory default settings but many people said it bricks your iphone, so I was worried. I stumbled upon a new technique and wanted to verify if this will work. I formatted my computer so now itunes wants me to sync it but it wants to erase all data first before it sync's it. If i click erase and sync, will it brick my iphone or just restore it to the iOS 4.2.1? I know iOS 4.3.3 is already out but i am not interested in updating at this point. Will this technique work or is there a better way?