FixWU

Safely resets a stuck Windows Update download queue. It checks for problems
a reset can't fix, backs up the update caches instead of deleting them, and
tells you what actually worked.

1. Checks for causes a cache reset can't fix (pending reboot, disabled
  service, WSUS / blocking policy, paused updates) and reports them.
2. Clears the BITS and Delivery Optimization download queues.
3. Stops the update services, then renames SoftwareDistribution and
  catroot2 to *.old. Windows rebuilds both; the .old copies are your undo.
  A backup left by an earlier run is replaced, so there's only ever one.
4. (Optional) Resets the WinHTTP proxy and Winsock catalog.
5. Restarts only the services that were running before.

Once updates work again, run it with -Cleanup to delete the .old backups.