How should I implement an auto-updater?

Question

Many programs include an auto-updater, where the program occasionally looks online for updates, and then downloads and applies any updates that are found. Program bugs are f

Answer 1

The simplest solutions (used by many programs) is running the uninstaller for the previous version and the running the installer for the new one (optionally skipping questions which the user has already answered, like the EULA). The only catch is that the new version must be able to read the configuration options from the old version.

Also, on Windows you can't delete an executable file which is in use, so you probably will want to drop a small executable in Temp folder, which runs the whole process and then delete it at the end from the instance of the new version which got launched (or just register it to be deleted at the next reboot).