I’ve accidentally deleted the “All Systems” Collection. How do I recreate it without re-installing ConfigMgr?

Contributed By: Cliff Hobbs [MVP ConfigMgr/ SMS]
As detailed in "Setup Command Line Options" section of the ConfigMgr TechCenter if you run Setup.exe with the “/NODEFAULTCOLL” switch then Setup will only create the “All Systems” Collection and none of the other default ones.

Re-applying a Service Pack will also recreate the default Collections as detailed in the How do I restore the default ConfigMgr Collections? article.