Although Microsoft didn't announce a notification center as part of the Windows 10 Technical Preview, a new hack can enable the feature in semi-functional form.
The hack, cobbled together by Twitter user Adrian and reported by Neowin, requires users to download a ZIP file with some third-party code, and to extract and run the included EXE patch. It certainly sounds a bit sketchy, so don't even think about it unless you're running Windows 10 in a virtual machine. Both 32-bit and 64-bit versions (warning: direct links to ZIP files) are available if you're feeling adventurous.
Just keep in mind that much of the functionality doesn't appear to be working. Running the patch doesn't create a shortcut on the taskbar, so users need to reload the patch every time they want to view the notification center. The types of notifications that appear may also be limited, or they may not appear at all.
Still, the hack is a sure sign that Microsoft is planning to add a notification center in Windows 10 down the road, as the feature also appeared in earlier leaks. Microsoft has said that it will tell the “consumer story” for Windows 10 early next year, so expect to hear more about notifications and other end user features then.
Why this matters: Notifications have become a key feature on other operating systems such as iOS, Android and Mac OS X, and it's one area where Microsoft is behind. In Windows 8, notifications only appear as one-time pop-ups, so there's no way to review all the ones you've missed. It seems likely that this will change as Microsoft continues its operating system overhaul with Windows 10.