If you've checked your Windows Phone 7.5 device for the 7.8 update with no success, you may want to try to force the process, just as we did with other Windows Phone updates like Mango. This is a little different than downloading and installing Windows Phone 7.8 manually, which we reported on earlier. With this method you're basically tricking the Microsoft servers to recognize your Windows Phone and initiating the update early. Think of it as cutting in line (and Microsoft is okay with this, no worries). The other benefit with this method (versus the CAB one) is it means you are getting the official carrier/OEM update that usually includes the firmware too. If using just CABs you are updating the OS but not any device specific software. That's not a bad thing but it's really not ideal. Best VPN providers 2020: Learn about ExpressVPN, NordVPN & more

How to Forcing requires patience and the ability to disconnect your computer from the internet. Make sure you have the Wifi and your data connection turned off on your Windows Phone and connect to Zune. Go to settings and check for an update and as soon as you click the "Update" link in the settings you'll need to disconnect from the internet. Let Zune come back and tell you that it can't check for an update right now, reconnect to the internet and you should see that an update is now available. Timing seems to be key and it may take you a few tries to get things just right (took me six tries). From there you follow along with the update wizard and your Windows Phone is updated.