SYSTEM REQUIREMENTS
If you want to upgrade to Windows 10 on your PC or tablet, here’s what it involves.
Latest OS ~ Make sure that you are running the latest version, either Windows 7 or Windows 8.1 Update.
Processor ~ 1 gigahertz (GHz) or faster processor or SoC
RAM ~ 1 gigabyte (GB) for 32-bit or 2 GB for 64-bit
Hard disk space ~ 16 GB for 32-bit OS 20 GB for 64-bit OS
Graphics card ~ DirectX 9 or later with WDDM 1.0 driver
Display ~ 1024x600
UPGRADE EDITIONS
Upgrade from Windows 7
From Edition To Edition
Windows 7 { Starter , Home Basic , Home Premium } ---- Windows 10 Home
Windows 7 {Professional , Ultimate } ---- Windows 10 Pro
Upgrade from Windows 8
Windows 8.1 ---- Windows 10 Home
Windows 8.1 {Pro ,Pro Student , Pro WMC } ---- Windows 10 Pro
Note:- Windows 10 Upgrade available from 29 July 2015