I have struggled for weeks trying to use the client to update my w810i. I have tried using virtual PC and Guest PC and both failed to work.
I now have the solution and have just updated by orange branded w810i to a generic w810i
The answe is very very simple - you need virtual PC and then you simply need to follow these instructions to make it work (You also have to follow the client instructions to flash your phone which can be found elsewhere on the forum or on Davinca web site)