Which Operating System should i use?

If i have two computers at home and thinking bout installiing a third. One system is running one Windows 95 and the other Windows NT and the computer at home is previuosly not networked and itend to network them when i install the third computer. I would like to be able to use the programs i already installed as well as newer programs, and i want to be able to install new hardware devices easily. Which OS should i choose for the new computer? Will i keep the present OS’s on the existing computers?