Bhav
 
Windows 10 is a free upgrade for owners of windows 7 and 8. As I owned both of those, I got it twice for both my mega PC and cheapskate backup PC.

Are you sure it is still? Mind sending a link? 
Still though - mine's an OEM license, which means I won't be able to use/transfer the license to another motherboard because it's tied to the motherboard it's originally installed on. Knowing that, I'll just have to go ahead and bite the bullet and shell out the $100.