You may also want to follow the windows system defender remove guide below from 2-viruses.com to delete Windows System Defender.
Free Windows System Defender Removal

Stop and remove Windows System Defenders virus processes:
WS064.exe
WS83b.exe
FS.exe
SICKBOY.exe
Disable Windows System Defender DLL files:
mozcrt19.dll
sqlite3.dll
ANTIGEN.dll
cid.dll
ddv.dll
exec.dll
ppal.dll
Delete these Windows System Defender fake av registry entries:
HKEY_CURRENT_USER\Software\Microsoft\Windows\CurrentVersion\Run “Windows System Defender”
HKEY_CURRENT_USER\Software\Windows System Defender
HKEY_LOCAL_MACHINE\SOFTWARE\Microsoft\Windows\CurrentVersion\Uninstall\Windows System Defender
HKEY_LOCAL_MACHINE\SOFTWARE\Windows System Defender
Remove the following [...]

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