Just a quick how-to this, many people get infuriated by Windows Defenders "interventions", either through it doing something they don't want it to or because they have a weaker system and WD just saps too much from their CPU for the system to run smoothly, for example on something like a lowly 1GHz AMD C-50 WD will choke it with pretty much 100% utilisation whenever the service is doing something. Supposedly Microsoft have made disabling Windows Defender in W10 21H2 "mission impossible", they really haven't, you just need to know the weak thread to pull at and we are going to do just that in this quick how to.

The biggest hurdle you need to get around is not being able to stop the anti-malware service, even registry edits won't do it the way the way this service now behaves almost acts like malware itself as even Safe Mode isn't safe from this service, so how do you stop it? Install Windows on another drive or partition (yes this really is the easiest way lest you want to jump through 20-odd hoops attempting other long-winded workarounds), after install;

1. Go to Control Panel > File Explorer Options > View > Select the box for "Show hidden files, folders, and drives", click "OK".
2. On the drive with the Windows install you want to use go to C:\ProgramData\Microsoft
3. Right-Click Windows Defender > "Properties" > "Security"
4. Now you need to take ownership of the files, click "Advanced", then "Change" in the next window
5. In this new window at the bottom type; Administrators then click "Check Names"
6. Click "OK" in all the open windows
7. If you haven't already install the registry entry to add "grants administrators full control" to the right-click context menu, do this for the Windows Defender folder
8. You can now delete or rename this folder to prevent Antimalware Service Executable from running

If you want to keep things this way you'll want to disable WU otherwise you'll have to go through these steps again with each major Windows update so disconnect from the internet the first time you switch back to your main Windows install to disable Windows Update through services.msc. Thats it folks, enjoy being free of Microsofts built-in Windows malware.