Contributed By: Garth Jones [MVP ConfigMgr/ SMS]
Are you like me have you accidentally deleted the “All systems” collection instead of a PC? Have you wonder how to get it back?

Well after some digging and asking around, I finally determine the answer! (with being pointed in the right direction)

<Drum Roll>

Install / Reinstall the last service pack!

BTW This might work in SMS 2003 too. If you try it and it works please let me know.