My power up wont complete. Why?

I droped my htc evo 4g in a bucket of water while working. 20mins later I discovered it. Surprizingly it was still powered on. I immediately disassembled my phone (removed battery, memory card, and unscrewed the 6 screws and took the back off. I placed every piece (except the screws) in a bowl of rice and left it sit for 24hrs. I put the phone back together and when I power the phone up it goes no further that the bright white "HTC" screen. It stays stuck there. Can anyone tell me what part of my phone needs replaced or if I am wasting my time and need to purchase a new phone all together....