Microsoft has started taking pre-orders for its new Windows 8.1 operating system (OS), ahead of the software's launch on Oct. 18.

Windows 8.1 is expected to fix at least some of the headaches Windows 8 has caused. The new OS has been in the works for quite some time and one of the most anticipated features it has to offer is the return of the familiar Windows Start button.

Consumers interested in upgrading their system from Windows 7 (or an older version) are now able to pre-order the latest Windows OS from the Microsoft Store. When it comes to pricing, Microsoft announced last month that the Windows 8.1 upgrade package would cost $119.99 and the Windows 8.1 Pro upgrade will be available for $199.99. In the UK, the upgrade packages will cost £75 and £125, respectively.

Meanwhile, those who are already running on Windows 8 will automatically receive the latest Windows 8.1 as a free upgrade.

"If you're running Windows 8, visit the Windows Store for a free update to Windows 8.1 starting on October 17," reads the Windows 8.1 pre-order page on the Microsoft Store. "If you're running Windows 7, your files will easily transfer. If you're running Windows Vista or earlier, qualify for the free upgrade to Windows 8.1 by purchasing Windows 8 now."

"The new Windows 8.1 lets you watch movies or play games with Xbox, Skype with friends, access files anywhere with SkyDrive, or find your next favorite app in the Windows Store. If you're already running Windows 8 you'll be automatically upgraded to Windows 8.1 for free on October 17. If you're running Windows 7, pre-order Windows 8.1 now."

The latest version of Windows will launch as the first major update for Microsoft's new operating system. Windows 8 was not as well-received as Microsoft likely hoped for, with users complaining about the confusing OS and the absence of the old-school Start button. The company promised to take user suggestions into consideration and try to fix things with a subsequent update. Windows 8.1 comes as that much-anticipated update, but it remains to be seen whether it will manage to iron out all the kirks that annoyed Windows 8 users.