iPhone restoring problem

Hi, my iphone 3GS stuck in Recovery mode after i'm trying to upgrade it into iOS 5. it says that an error occured so it cannot restore. once i tried to connecting with itunes, it detects The iPhone but NOT my iphone, and 'restore' button is the only thing that i can hit, but it failed to restore either. I've been trying (maybe a hundred times) push Home and Power button then release only power button after it shuts down and release the home button after about 20 seconds but it still won't affect anything. i also remove my itunes then i redownload it again, but it won't detect my iphone. anyone can help me? i'm desperate. all my college works, contacts, important notes is in there. i also browsing about my problem on google but every solution they suggested failed to moved my iphone to break from his silence.