Newegg has the Microsoft Windows 8 Operating System Software, 64-bit OEM (WN7-00404) for $100 - $20 off with coupon code EMCYTZT2618
[Exp 12/9] = $80
with free shipping. Normally $100. This is the full-version software, but OEM is intended for new systems and cannot be transferred to another computer once it is installed.