IPhone 3GS won't power on

I have an IPhone 3GS running iOS 5.0 and have the following issue:

When i plug it to the wall with the charger is powers on, but it tells me that I have to connected to iTunes. But when I connect the phone to the computer there are no changes on my USB ports and the phone does not power on anymore.

I have tried connecting it to my Win7 laptop and WinVista desktop to no avail.

When I do get it to power on connected to the wall, I do see a percentage on the battery, so it might be a battery issue, but I don't know.

Any tips, or ides are really appreciated as to how to get the phone up and running again.

Thank you.