Com Port Problem

Hello comrades,
I have 2 uno devices I am using for a project. One connects without a problem but the other one does not. Under the tools menu ports is greyed out. The good board doesn't have this problem at all. I have opened device manager to make sure my computer is actually seeing the board and it is (it identifies that it is an uno and in com 4.) This unfortunately doesn't seem to be a case of obvious configuration settings that have been missed (baud rate, type of board used in program tools menu, etc.) Any ideas?

Are they truly IDENTICAL board ?

Do you have anything connected to them ? (especially pins 0 and 1)

Thank you for your response Bob,
yes they are as close as a massed production model can be to one another. I am aware that pins 0 and 1 are also used for serial com and that they can cause some funking stuff when connected. I just got the solution right now. It appears the driver did not configure properly for the one board. I just uninstalled the arduino software and reinstalled it. If you have a similar problem try doing this. Again thanks Bob and a karma point for you good sir.