What exactly are all those accounds registered in Net User??

Administrator ASPNET
Guest HelpAssistant SUPPORT_388945a0

all of these are in there, why is this? What is there purpose?? Is it safe to delete the ones i dont use?

net user Administrator is a built-in account for administering the computer/domain
net user Guest a built-in account for guest access to the computer/domain
net user HelpAssistant is a Remote Desktop Help Assistant Account.
net user SUPPORT_388945a0 is a This is a vendor’s account for the Help and Support Service.

You cannot remove the Guest and Administrator account.

ASPNET is part of the .NET system.

Cannot locate anything concerning SUPPORT_fzzfa904. I can only assume it is another account system created.