Windows XP taskbar not showing up

This is a practical post to document a Windows XP problem a friend of mine has had. I did not found the solution in Google and thus it should be useful to put it somewhere.

This friend called me because when logging into Windows XP, just the wallpaper was shown: no taskbar or icons appeared. I told her to run "explorer.exe" from the task manager, but the taskbar just flashed in and out. One thing however: before executing anything from the task manager, an error dialog telling something about some Google file missing was shown.

We opened regedit and looked for Google and found the UninstallString of Google desktop and ran it. Apparently the deinstallation succeeded and the error dialog disappeared, but the taskbar still won't show up.

I end up going to my friend's home and trying deinstalling more things ("XP Styles", an antivirus), deactivating shell extensions, running Ad-Aware, using Process Explorer and FileMon and RegMon, restoring XP to an older saved state, and nothing worked.

Just before resorting to repariring the XP, I thought of looking back to the original Google desktop problem. I intended to delete any traces of the Google desktop directory and reinstalling it again, but in these directories I already found "GoogleDesktopSetup.exe". I ran it, rebooted (or maybe just logged out and in again), and there was the taskbar.

So Google desktop broke somehow (have no idea of how) and after that Explorer did not start properly, even though Google desktop seemed to have been deinstalled, and the problem was not fixed until Google desktop was installed again. A pity that a so well-famed company as Google causes that kind of problems. I hate when something fails without saying anything about it.

Hope this helps somebody