Are grounded outlets for home theater power conditioners really necessary?

[NDallasPunk]

My house is very old and my power conditioner states that the outlet is not grounded and my hot and cold wires are reversed. The sound is great though and all electronics are functioning as normal. This makes me wonder how necessary the grounded outlet really is. I would rather not call an electrician if this is truly a minor issue. Any advice would be greatly appreciated! Thank you!