Have you talked with the people that you bought them from?

I just bought the house and the previous owners do not remember who replaced the windows.

They have moulding strips around the pane and I am hoping to simply install hardware to make the windows open.

I would prefer not to replace the entire window with a movable assembly since these are new and well insulated. Is this possible?

The short answer is NO.

The amount of labor involved versus the quality of the finished product leads me to recommend replacing the ones you want to open.

My mistake, I misunderstood the original question. I thought you meant that you bought new windows (operators) and they weren't working correctly.

You have fixed windows that you want to convert. In that case, I agree 100% with Lollygagger that that is not something you want to do.