A lot of I.T gurus agree that Linux is the most powerful Operating System out there. Linux is used by lots of big companies for its reliability, security and almost limitless power.
My favorite distro for browsing, simplicity and basic learning would be Linux Mint. You can really achieve almost anything on it. I recommend reading an article that will guide you with the Linux basics or terminal commands.
Gparted - Used to partition hard drives
Kali Linux (Penetration Testing, requires some practice and reading)
EasyRE (Great tool to fix boot issues with Windows, had great success with it)
Parted Magic (Awesome all in one Linux distro that includes Partitioning, Cloning, Rescue, and Erasing)
VMWare vSphere Hypervisor (Best Virtualization solution for servers/workstations out there. Offers free license!)
I'll be adding more useful distributions soon!