New
#11
Actually, no reboot is necessary to update the registry. The reboot is necessary to replace files that are in-use at the time the application is installed (such as with a newer version).
Some apps always say you have to reboot, even though they've done nothing that requires it. Some apps are smart and only reboot if it is actually needed. It's hard to know which kind of app you're installing, so it's usually best to just reboot.
With Windows System updates, if it says a reboot is required, then it's generally the smart kind. It knows what it's done, and it knows if you need to reboot. However, you can typically continue using Windows and let the automatic reboot happen at 3am or whatever time you specify, or simply just wait until you shut down for the day. Be aware, though, the issue the update is fixing may not be fixed until the reboot occurs.