Windows Server 2008 R2 Core activation by phone

Here is a very good manual, how to activate Windows Server 2008 R2 Core by phone.
Short summary:

1. Enter product key: Cscript.exe %systemroot%\system32\slmgr.vbs -ipk
2. Get installation ID: Cscript.exe %systemroot%\system32\slmgr.vbs -dti
3. Get phone number to receive the activation ID: notepad %systemroot%\system32\sppui.inf
4. There' a bug in the original article - the filename to get the phone number is wrong
5. Choose and call the phone number, follow instructions, receive activation ID
6. Write down the activation ID received by phone (ideally write it directly to a notepad window to copy and paste then for product activation
7. Activate product using: Cscript.exe %systemroot%\system32\slmgr.vbs –atp
8. Verify product activation: Cscript.exe %systemroot%\system32\slmgr.vbs –dlv
9. Enjoy!