Microsoft is getting a jumpstart on sales of its Windows 8.1 operating system, which is now available for pre-order.

Those already running Windows 8 can sit tight — you can upgrade for free later this month. But Windows 7 users can now get a head start on the upgrade process via Microsoft’s online store.

Windows 8.1(Opens in a new window) and Windows 8.1 Pro(Opens in a new window) will cost $119 and 199, respectively, which falls in line with the current pricing structure for Windows 8.

Windows 8.1 marks Microsoft’s first major update to Windows 8, which was released in October 2012. The incremental upgrade includes more personalization, Internet Explorer 11, Bing-powered search, built-in apps, an improved Windows Store experience, and cloud connectivity with SkyDrive.

The Pro version, meanwhile, includes enhanced security features, plus the ability to host a remote desktop connection or connect to a corporate or school network.

Windows 8.1 is scheduled to arrive first in New Zealand at 12 a.m. local time on Oct. 18, which is 4 a.m. on Oct. 17 in Redmond and 7 a.m. on the East Coast.

“One shift to note in Windows 8.1 is that we will be offering ‘full version software’ at retail and online for download that does not require a previous version of Windows in order to be installed,” Microsoft said in a recent blog post. “This shift allows more flexibility for customers in specific technical scenarios and is in response to feedback we’ve received.”

Customers looking to purchase a new PC with standard Windows 8.1 will be able to upgrade to Pro for an added $100.

Redmond released a preview version of 8.1 at its Build developer conference earlier this year, and sent it to manufacturers in August to allow OEMs to pre-load Windows 8.1 on devices for release ahead of the holiday season.

The updated OS was not designed for installation on devices running Windows XP or Windows Vista. But if you truly have no other options, Redmond recommended getting the DVD and doing a clean install.

For more, see PCMag’s Hands On With Windows 8.1 Preview.