Nokia has started global roll-out of Windows Phone 7.8 firmware update to first generation Nokia Lumia devices, which is currently available for selected regions. Well, if the update is not live in your region, don’t worry, their is a trick to force the update to your device.
Step by step instructions to force the Windows Phone 7.8 update:
Connect your Windows Phone to a PC and launch the Zune software
Click on Phone > Settings > Update. Allow the software to tell you whether an update is available. If so, skip this guide. If not continue to the next step.
Time to force the update. Click another button (any of the options above or below the word Update). Then click the Update button again, and this time disconnect your computer from the internet after 1-2 seconds. Do this by pulling out the Ethernet cable, disabling Wi-Fi, etc. If it says your phone is already up to date, you didn’t disconnect quickly enough and need to try this step again.
Wait 30 seconds or so and Zune should display a notification that an update is available.
Now reconnect to the internet and continue with the update process through the Zune software.
Depending on what OS build you are starting with, you may be prompted for several OS updates
Let the phone update and wait. The final OS build is 8858. If you are getting just 8779, you’ll want to repeat 1-4 above
You may also be prompted to install a firmware update at the very end, follow through with this
Celebrate! The whole process, including backup could take up to 60 minutes. Check that you are on build 8858 to see if you are done.
What if this method just doesn’t work?
If you don’t get the update, that means your software update is literally not on Microsoft’s servers for your phone/carrier. Try again in a few days.