Oh God, please don't replace your windows! All they need is a good reglazing, and maybe some weather stripping if it gets really cold. Properly maintained windows are energy efficient. Removing your windows will destroy the architectural integrity of your house. It will be very hard to find the perfect replacement window for this size.

Those window are the only thing your façade has going for it. I'd put another set on that bare wall, too.

Find a licensed contractor and replace them. Single glass windows are not good for anything.

Thanks, Jennifer (I don't know Feng Shui...I have my own version of it, though)

BTW, ali mayea, check with your local building dept. to see if your local building codes will let you replace these (if you go in that direction) without having to raise the sill to 18". Here, in NYS, there's restrictions that may require one to raise the sill on replacements for double hung and casement windows.