Windows 8 upgrade is on sale for one more day! If you buy the upgrade, you can run it later.
Starting tomorrow, the price for a  Windows 8 upgrade  jumps to $119.99 for the standard edition and $199.99 for the Pro version.
This is for a computer with a version of windows already on it (not for a home built PC or new hard drive)
Click the image or the link below to go to the upgrade page
windows 8 upgrade page
If you need the OEM version, it's on Newegg for $100