Lumia 900 Firmware V.3.81 RX51
Free download Lumia 900 RX51 Firmware V.3.81.
Using the Links and Video posted here, you can download, install and run the Nokia Care Suite software. This software allows you to download the Latest STOCK OEM ROMs directly from Nokia Servers. It also allows you to flash these ROMs to your Nokia Phones. Keep in mind, this WILL WIPE YOUR PHONE CLEAN! So, be sure you have a backup of all your data, photos, videos, texts messages, etc... EVERYTHING
PS: Use these at Your Own Risk! I will not be held responsible if you destroy your new Lumia with these. With that said, I've flashed my own Lumia 900 8 times and my Lumia 920 3 times with no ill effects.
DOWNLOAD THE LATEST VERSIONS FROM HERE:
Download Nokia_Care_Suite_PST_5.0_2012.51.4.4.zip from mirrorcreator.com Use this to flash or Unbrick your phone.
Download Nokia_DataPackage_Manager_2012.18.0.zip from mirrorcreator.com Use this to download Multiple ROMs. NOT needed, as Care Suite will download individual ROMs.
Running Windows 8?
You must edit the Registry to Enable installing MSI Files as Administrator, then you need to right click on the installer file and select Run as Administrator. You can use the manual method to install the Registry edit, or you can download and run the file to install it.