Below are resources for Windows 10 to help facilitate updating from WIN7 or WIN8

http://www.microsoft.com/en-US/windows/windows-10-specifications

http://answers.microsoft.com/en-us/insider/wiki/insider_wintp-insider_install/frequently-asked-questions-windows-10/5c0b9368-a9e8-4238-b1e4-45f4b7ed2fb9

If you want to upgrade to Windows 10 on your PC or tablet, here’s what it takes.

* Latest OS:  Make sure you are running the latest version either Windows 7 SP1 or Windows 8.1 Update.
*  Need to download the latest version? Click here for Windows 7 SP1 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:  1024×600