Apple’s factories have garnered quite a lot of attention over about the past year, largely because in 2013,  the company relocated some of its computer manufacturing back to the United States. As an American company,  early Mac models were made in the United States. However, throughout the 1990s, domestic labor costs eventually contributed to Apple’s decision to move its  manufacturing to Asia. Similarly,  according to Business Insider India, Apple’s factories have once again become the topic of viral discussion. Though, this time, it has nothing to do with labor costs and everything to do with Microsoft.

On Friday, Apple CEO, Tim Cook, walked walk through the company’s Forth Worth, Texas factory, and tweeted a few photographs. In one photo, a pair of Mac Pro computers are in the background, unmistakable in their silver aluminum bodies with small black Apple logos. Yet, beyond those definitive aesthetic characteristics, the Mac Pros actually do not look like your average in-operation Apple computer. Why? Because they are clearly not running Mac OS X.

Instead, the computers appear to be running Windows. The computers each have multiple tabs open, each with the unmistakable blue trim of the Windows operation system. Upon zooming in, you can almost make out the Windows start menu icon in the lower left-hand corner of one of the screens.

Why is a factory manufacturing Apple computers also using the software of one of Apple’s biggest competitors? That much remains to be seen, but you can bet that Microsoft will have a field day with the news.

Photo credit: Twitter/tim_cook