Download the latest version of 9810 handheld software here:
Once downloaded, install it onto your computer. Obviously make sure you also have blackberry desktop manager installed as well.
Now either search your C drive, including all hidden files and folders, for files called "vendor.xml" - once the search is complete, delete all instances of the results. Or, manually navigate to these locations and delete each "vendor.xml" file you find:
C:\Program Files(x86)\Common Files\Research In Motion\AppLoader
C:\Users\Me\AppData\Local\VirtualStore\Program Files (x86)\Common Files\Research In Motion\AppLoader
C:\Users\Me\AppData\Roaming\Research In Motion (check each folder)
Search for and delete all "vendor.xml" files found in the above 3 locations, or from your C drive search results prior to updating your operating system using "apploader.exe" found here ->C:\Program Files(x86)\Common Files\Research In Motion\AppLoader <-.
Launch "apploader.exe", then connect your 9810 to the computer without it's battery, once the pin shows up in "apploader" drop down menu, you should click next to proceed.
If everything worked like it did for me, twice, on my own 9810, then you will be able to install the operating system and fix your phone.