Upgrade Virtualbox in Win7 64bit failed from 3.2.6 to 4.1.8

[kennyw]

My Win7 machime is Dell OptiPlex 980 type, and I have used VirtualBox 3.2.6-63113 for a long time. Last week, I tried to upgrade to 4.1.8-75467 {I didn't uninstall Virtualbox-3.2.6 first, instead I only downloaded Virtualbox-4.1.8-75467 and double click the .exe file dirctly. I know I'm stupid not to uninstall old one first, but I do concern it will uninstall my original configure files about virtual machime.}, but it throwed out a warning Window "Installation failed! Error: Fatal error during installation.". After that happened, I could not reinstall Virtualbox-3.2.6 as well. I tried to use MS's Fix it tool and search history tickets, but no results. Attached file is my VBox log file Windows log file. Please help to check the root cause, any hint is very appreciate, many thanks!