The latest video shows that Nelson has now installed a second hard drive inside the Steam Machine and has installed Windows 7 Enterprise, allowing the device to boot and run both operating systems. Nelson also ran 3DMark benchmark demos on the Steam Machine with Windows 7. The high end Fire Strike demo scored a 7858, which according to 3DMark is a little slower than a high end gaming PC mark of 9131. The Steam Machine"s benchmark is still better than 70 percent of all PCs tested by 3DMark.
The demo shows that third party Steam Machines will likely be able to run Windows 7 in addition to SteamOS with little problem, which might be a big selling point when they go on sale sometime in 2014.
Source: Corey Nelson