There are many free linux live CDs available on the net, for example, Hiren's Boot CD, Ubuntu Live CD.

In Windows, you can open the Task Scheduler to create a scheduled task to perform the restart.
To restart, run the following command/script at the command prompt:

shutdown /r

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Another way of disabling PIN is delete this folder: C:\Windows\ServiceProfiles\LocalService\AppData\Local\Microsoft\NGC
You might take ownership of the NGC folder before you can delete it.

Boot from a linux or ubuntu live cd and you can delete any files.

Check all the Desktop folders for all your user accounts under C:\Users, I hope you can find all your icons somewhere.
When Windows fails to load your profile normally, it will automatically create...

It's likely that your administrator account is disabled after upgrade. Use the Option 4 described in the following tutorial to enable your admin account:
Administrator account - Enable or Disable in...

Check out this tutorial. Copy the entire folder C:\Users\<user_name>\AppData\Local\TileDataLayer from a newly created account, and then replace / overwrite the TileDataLayer folder of your target...

It should be a profile issue and you're logged in with a temporary profile.
Go to the C:\Users\<user_name>\Desktop folder, check if your desktop icons are there.

Have you tried this registry tweak?
Navigate to:

HKEY_LOCAL_MACHINE\SOFTWARE\Microsoft\PolicyManager\default\Settings\AllowSignInOptions

Create a DWORD 32-bit Value named value, and set it to...