Andrew,

wupdate.exe does not require a machine reboot . wupdate.exe (the web update client) checks if an update is available. If this is the case, it downloads and executes your "web update installer package". This package seems to update files that are "in-use" (locked) and so Windows requires a reboot to complete the install.

I would suggest to make sure that the application to be updated is not active (in-use). There are several built-in functions in the installer to handle this. If the update installer package detects that the application is still active, display a message and ask the user to terminate the app.

Does this help?

Friedrich