Not Working, Not Responding

Hi,

I dropped my iphone 3g recently and cracked the digitizer and broke the lcd, so I bought a new lcd + digitizer and a new white housing cover for a change.. when everything was put together the iphone does nothing, black screen doesnt respond on a coputer. but i tried charging it but nothing happend but then took the battery and check if its still alive and it was, had 3.69 V to it...

Also from the fall there was n little scratch on the back of the MotherBoard on the edge on the Silver/grey sticker???

Can anyone help me?? im stuck and frustrated!!!

cheers