Dell, Acer, Samsung, Asus, Sony, Hewlett-Packard and Lenovo are some of Microsoft's partners that have built computers to run Windows 8.
Sinofsky also announced the grand opening of the Windows online store where it will sell applications and media content, much like Apple's iTunes store does. The store will run in 231 markets and in 109 languages. While Sinofsky acknowledged that the Windows Store may not have as many apps as other app stores, he said that hundreds of apps are being added everyday.
Microsoft also showed off its Surface tablet, which runs on Windows 8, at the event. The mobile device hits store shelves Friday and is priced at $599 with the touch keyboard cover.
The Surface features a camera on the front and back, comes installed with the Office software, and will run Windows RT, a version of Windows 8.
"Windows 8 PCs really are the best PCs ever," Ballmer said. "Windows 8 really does bring together the best of the world. PC, tablet, work and play."
The launch of the Surface tablet is the latest in a series of new tablets over the last several months. Google introduced its new Nexus 7 during the summer. Amazon's Kindle Fire HD was unveiled in August and Apple just took the veil off its iPad mini Tuesday along with its fourth generation iPad.