In this chapter, we discussed how to read from and write to the Windows Registry at install time. Reading stores a value from the registry in a Windows Installer property that you can then use elsewhere in your markup. Writing is done with the RegistryKey and RegistryValue elements. The former is used for writing multiple values and the latter for writing a single value. You have the option of setting permissions on these values and specifying whether or not to remove existing keys that weren't included in your MSI.
In the next chapter, we'll cover how to interact with Windows services. WiX gives you the capability to create, start, stop, and remove services. We'll also see how to configure a service's user account and recovery options.