Thanks to Martin Brinkman over at ghacks.net, I was reminded of two important Windows 8 related expiration dates for this month. First, and probably foremost for most readers, the $40 to Windows 8 Pro upgrade offer expires on January 31, 2013. This is a great deal for machines with a valid Windows OS already installed, where you can exercise it directly from the PC you wish to upgrade on as many PCs as you like, all for the same charge. You can even download the upgrade and wait to install it after the deadline, if you like. One potential gotcha to be aware of: if you download the upgrade from a 32-bit Windows install, you’ll get a 32-bit install image for Windows 8. Since most people will want to download and install the 64-bit version, no matter what version they’re currently running, be sure to run your download from a 64-bit machine!
The other expiration date hits in mid-January — the 15th of the month to be precise — and it’s for any and all of the Windows 8 Preview versions (Developer/Build 8102, Consumer/Build 8250, and Release/Build 8400). My guess is that if you grabbed any other builds through “alternate channels” (such as BitTorrent) they will also go bye-bye at the same time. Just for the record, a legit copy of Windows 8 shows a build version of 9200, so anything less than that number is probably subject to the turn-off by the middle of this month.