IPhone 3GS dead and not turning on, hot?

I have an iPhone 3GS that died while on charge, the last I saw it was on 70% - 80% battery.
It doesn't turn on at all and I get no response from it. I've tried a hard restart and other reset methods as I have read online, but nothing works.

I replaced the battery and nothing has changed. I had it on an iPod dock and all it did was get hot.
Upon plugging it into a computer I got a message saying:
"USB device not recognised
One of the USB devices attached to this computer has malfunctioned, and Windows does not recognise it. For assistance in solving this problem, click this message"

Is there anything I can do to fix it? Or is it beyond repair?

I had the same phone (3GS) for 3 years and the buttons stopped working after a while, things broke off from the plastic casing and it loosened up. They are not built to last.

I don't really think there's much you can do if you said you have already changed the battery. Also if you say your phone is becoming really hot and is non responsive then it could mean that there's something wrong with the inner workings of the device. The only thing I can thing of is maybe try and take your device into your local phone store or even one of those phone stalls in the centers and see if they can recover your phone otherwise I think it may be time to get a new one.