Microsoft just sent out invites to its Oct. 25 press event in New York City, where the Redmond-based company is expected to unveil its Windows 8 operating system.

The official request asks invitees to "save the date" and reads "You're invited to celebrate. Windows 8." Details of the venue or time are not mentioned. The agenda for the event too is shrouded in mystery, but it is widely anticipated that Microsoft will be announcing its latest OS in tandem with the launch of its Surface Pro and Windows RT tablets.

"The next version of our operating system, Windows 8, will be generally available on October 26, 2012. At that time, we will begin selling the Surface, a series of Microsoft-designed and manufactured hardware devices," Microsoft revealed in its annual report in July.

Microsoft CEO Steve Ballmer stated that "Windows 95 was certainly the biggest thing in the last 20 years" but Windows 8 surpasses the OS without a doubt.

Reports have also suggested that Microsoft is expected to build more than 3 million Surface tablets. Microsoft also revealed that it will have 32 holiday pop-up stores in Manhattan this fall, and in an interview to The Seattle Times, Ballmer confirmed that the Surface tablets will be sold at the pop-up stores.

Ballmer also asserted that the 2013 PC market will be a big one with close to 400 million PC sales and Windows 8 would play a major role in fueling the sales figure.