I have tried multiple times to upgrade my Windows 10 (Build 10240) Dell XPS8900 PC to the anniversary edition only to have the update fail with the error 0x80073B92 – 0x20009. It says the system failed in the safe_OS with an error during prepare_rollback operation. I get the message when the computer restarts and always have Internet Explorer ask if I want to use new settings or use existing settings. I should note this computer dual boots Windows 10 and Windows 8.1. I don’t think the dual boot is the problem since I have a Gateway S5405D dual booting with Windows XP and Windows 10, a Gateway FX530XM dual booting Windows 7 and Windows 10, and a Dell XPS8500 dual booting Windows 8.0 and Windows 10. The other three computers did the anniversary update successfully with no problems, it is only the XPS8900 which refuses to update the 10240. I attempted to lookup the problem on the Internet. I disconnected all the USB devices and tried without an Internet connection, only to have the same issue. Any advice would be greatly appreciated.