After leaving users of mobile devices running Window Phone 8.1 in the dark for quite some time, Microsoft is finally letting them see the light, announcing Thursday that it has started to roll out Windows 10 Mobiles to applicable devices.

This announcement is a major one for those who had an attachment to an older device or simply weren't willing to shell out the cash for a new one. To date, the only way to get access to Windows 10 Mobile was to either purchase a new phone with the OS pre-installed, or use unfinished software. This update eliminates that - for the most part.

In Micrsoft's announcement, the firm provided a link that leads to a page displaying all the phones and devices that can updrade to Windows 10. The supported phones are: Lumia 1520, 930, 640, 640XL, 730, 735, 830, 532, 535, 540, 635 1GB, 636 1GB, 638 1GB, 430, 435; BLU Win HD w510u, BLU Win HD LTE x150q; and the MCJ Madosma Q501.

As you'll notice, this list skews heavily toward devices built by Microsoft and Nokia, so if your cherished phone happened to be an HTC One M8, for example, you're out of luck. Additionally, the firm admitted that "many older devices are not able to successfully upgrade without an impact on the customer experience," so don't hold your breath if your phone does happen to be Microsoft/Nokia-made but isn't on the list.

Similar to Microsoft updates in the past, the availability will differ depending on the "device manufacturer, device model, country or region, mobile operator or service provider, hardware limitations and other factors."

If you meet all the prerequisites for the upgrade the method to update the device will stay the same no matter what. Once you free up enough storage space to download, simply plug the phone in, connect to Wi-Fi and let the updater do its thing.

Microsoft's Upgrade Advisor app can help users figure out how to free up some space for the installation.

It should be noted that users should expect to see some changes once they upgrade. Not only will certain Windows 10 Mobile features like Continuum and Windows Hello not work because they're hardware dependent, but other features like Cortana or Me Tile and Me Card will either become lost or modified.

This is the second time Microsoft has botched an update related to Windows 10. The first time was when reports came in about peoples PC's upgrading to Windows 10 without any input.