We knew it couldn’t last. A Windows upgrade price of less than $40 seemed too good to last forever, and today Microsoft confirmed that suspicion, in an announcement(Opens in a new window) on its blog.

But you still have until Jan. 31 to take the plunge into the speedier, tile-happy new operating system for the low upgrade price to Windows 8 Pro of just $39.99 online for existing users of Windows 7, Vista, or even XP.

Those who bought new Windows 7 PCs starting June 2 through Jan. 31 get an even sweeter deal, with a $14.99 upgrade price to Windows 8 Pro. A DVD Windows 8 installer at local retail shops or ordered online from Microsoft costs $69.99.

After that, starting Feb. 1, you’re looking at $119.99 to upgrade to the standard, non-Pro version of Windows 8, and a hefty $199.99 for the Pro version. As a reminder, the Pro edition adds the ability to join networking domains, disk encryption, and support for Windows Media Center.

Speaking of Windows Media Center, existing users of Pro are currently able to add this for free within Windows via the “Add Features to Windows 8” feature—but also just until Jan. 31. For those who got regular Windows 8 PCs but want to upgrade to Pro, that requires the Pro Pack – $69.99 until Jan. 31, and $99.99 after.

Here’s a table that lays out the pricing changes ahead:

Though these prices are far steeper than what’s been available to this point (and than Apple Mac OS X upgrades of late), they haven’t gone up from Windows 7’s initial pricing.

Do-it-yourself system builders and those wishing to run the new OS in virtual machines will need the full, non-upgrade installer, aka System Builder editions. While the Microsoft blog post mentions the existence of these editions, it gives no indication of pricing, only noting that they’ll be available from online and local retailers. These editions are generally discounted, since you’ll usually be buying a motherboard or other system hardware together with them.

Microsoft’s TechNet site has a thorough run-through of what’s involved with all the upgrade scenarios online at a page appropriately titled Windows 8 Upgrade Paths(Opens in a new window). You can also check out your options using Microsoft’s Upgrade Assistant(Opens in a new window). For a deep dive into all the new capabilities and performance Windows 8 entails, read our full review of Windows 8.

For more from Michael, follow him on Twitter @mikemuch(Opens in a new window).