How to access Samsung Galaxy S2 storage while phone is off
what I would suggest is that you flash your device with Odin, your files such as mp3, pictures and videos would be untouched, basically every file on the internal SD memory would be untouched, if you have your contacts synced with Google you should be able to get it back. 

but this would void your warranty 

sorry I assumed you could boot into recovery or had hit a boot loop, this might not work but is worth a try, you could try clean the terminals on the phone and the battery (I have had instances where my s2 just wouldn't boot and this helped)