2x Apple iPhones - one 3G and the other 3GS, both 16GB. Not working

Apple iPhone 3GS 16GB model A1303A. Apple iPhone 3G 16GB model A1241. Apple logo appears but then turns off. Doesn't respond to charging or connecting to a computer. That's about it. The "connect to iTunes" screen appears but my PC doesn't recognise it.

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