Microsoft Remote Desktop Service (free)

Host -- Windows PC (both 32 and 64-bit) that can be remote accessed by Microsoft Remote Desktop Service:

• Windows XP -- Professional
• Windows 7 -- Professional, Enterprise, Ultimate
• Windows 8 -- Pro, Enterprise
• Windows 10 -- Pro, Enterprise, Education

Clients -- PC or devices that can used to remote access the Host via Microsoft Remote Desktop Service:

• Windows XP -- Any version is ok for connecting to Windows XP Host.
  • Special settings (MS TechNet) on the host or additional software (here) for connecting to Windows 7 or above.
• Windows 7, 8, 10 -- Any version is ok for connecting to any Host
• Android -- Microsoft Remote Desktop (here)
• iOS -- Microsoft Remote Desktop (here)
• Mac OS -- Microsoft Remote Desktop (here)
• Linux -- RealVNC Home Edition (here); free for non-commercial use only

RealVNC (here)

• Home edition: free for non-commercial use only, Limited to 5 remote computers and 3 users
• Professional and Enterprise also available with enriched functions