In case the installer fails to install/uninstall BestSync, you can use the following command to take a log file, then find what is wrong with the install process.
Please open the command prompt windows first by administrator privilege, then change the current directory to the folder where the installer file is.
1. Uninstall BestSync
msiexec.exe /l* install.log /x BestSyncSetup.msi
* install.log is the file name of the log file
* BestSyncSetup.msi is the file name of the installer file
2. Install BestSync
msiexec.exe /l* install.log /i BestSyncSetup.msi