Skype install error 1603 when updating to 6.0
tl;dr: Restart and run the installer again.
One morning Skype decided to update itself. However the upgrade failed with an install error 1603, and tried to make up for its crypticness by launching an automatic query of Skype's help centre, which turned up no results.
This left me in a completely broken state - Skype was no longer available for use. It turns out it had uninstalled itself before doing the update.
So what does this 1603 mean?
It turns out you can enable logging by Windows Installer using the registry key value voicewarmupx - no, this is not a joke in the vein of Joey Hess' April's Fool; each character enables a different logging mode, as explained in the same support page for earlier versions of Windows.
Re-running the installer, we get a MSI...log file in the %TEMP% folder. Soon it becomes clear the logfile is divided into two halves - lots of Executing op: RegAddValue lines at the front (corresponding to the install progress), and Executing op: RegRemoveValue lines at the end (the revert/undo, after the install runs into failure). A quick bisection turns up the root of the error:
MSI (s) (3C:44) [13:36:26:938]: Executing op: ServiceInstall(Name=SkypeUpdate,DisplayName=Skype Updater,ImagePath="C:\Program Files (x86)\Skype\Updater\Updater.exe",ServiceType=16,StartType=2,ErrorControl=0,,Dependencies=RpcSs[~][~][~],,StartName=LocalSystem,Password=**********,Description=Enables the detection, download and installation of updates for Skype.,,)
Info 1923. Service 'Skype Updater' (SkypeUpdate) could not be installed. Verify that you have sufficient privileges to install system services.
Very often, after deleting a service, it still shows up, and is completely gone only after a restart. Restarting, the installer ran to completion.
Moral of the story: if something went wrong, describe what went wrong - in detail!
