Logitech software is the WORST ever. I got a new keyboard and it WOULD NOT PAIR with my existing unifying receiver. The software kept telling me it could not find the keyboard, etc. I went through **** unpairing my old keyboard, then not being able to re-pair it, not having any keyboard, etc. etc. AWFUL EXPERIENCE. Then suddenly, the new keyboard is working, even though Logitech kept telling me it couldn't find and pair it. Logitech wasted several hours of my time today!!! The only reason I keep using Logitech is because I like its trackball mouse better than any other mouse on the market.