USB not working in Compaq Presario V5000

[VWgrubber]

Two USB slots on the side of my computer.  If I plug stuff into the top slot it will work perfectly, but when I attempt to use the same hardware in the bottom slot it doesnt read at all.  I have checked the Device Manager and it says they're both working properly, but clearly they are not.  I need both slots to work.  Can somebody please help me out with this?

[VWgrubber]

to update my original posting:

I have my External Hard Drive plugged into the top (working USB slot) and my MP3 player hooked up to the bottom slot.  My computer is not recognizing my mp3 player as being plugged in; however my mp3 player is charging through the usb cable.  hopefully this helps somebody figure this out.

[patio]

You will need to open the case to see how those USB headers are wired and if they are hooked up correctly...