Windows Booting very slow after 2004 update ,

You did not need to do the other  commands as it is consistent and in sync. I suspect the errors are due to other service dependencies, and it would need to be done from a "safe mode" boot. If you still have a long booting time then it is something else, maybe a large external disk or NAS that it is trying to check out during the blank screen phase?

It's not an external disk, so that's out of the question. Personally, I think we're all huffing and puffing & then the update will slide down the tubes and that will be the end of this conversation. 

Stay healthy man! Thanks for your efforts & helps!

Because 2004 is a bit immature and the drivers are not available yet for many manufacturers, if you see a similar issue, consider rolling back to 1903/09.

https://www.yourwindowsguide.com/2020/05/uninstall-windows-10-version-2004.html

@RoyGray731:" This is something you can easily try on your system.

If you want to turn it off, click on the Windows start prompt and type "Defrag".  Select the Defragment and Optimize Drives app.  For each drive, ensure that Scheduled optimization is turned off."

Many thanks for that interesting and useful observation. That could be one of the many things "getting in the way" and fighting with the "normal" expected performance during normal working of users systems. It is certainly worth trying, as modern disk really should not cause issues if the odd bits of fragmentation are there. In any event, I always thought the NTFS writes were queues and consolidated to reduce fragmentation anyway.

Your suggestion may well help those with your type of configuration.

@Sumit - while I am sure you are correct, that Feature Update 2004 is immature, these sorts of problems arising NOW is surely a reflection of insufficient testing and not using more diverse configurations., on the part of Microsoft. I know that certain Realtek Drivers  are causing issues, and that it is on hold for some configurations. Also the "Storage Devices" bug can stop the upgrade being offered. The printer issues were a commonly reported issue too, although it HAS had a fix.  Certain NVIDIA display drivers are also an issue. Those too should have stopped any install being offered.

Although it seems that Microsoft IS liaising with the major companies like NVIDIA, Realtek etc. you seem to be suggesting that there are many more problem drivers out there, that can cause performance issues.

Again, this comes back to insufficient testing of the diverse brands and config that can exist. Surely a company as large as Microsoft, MUST have some sort of verification "checklist" to go through (covering all the manufacturers and driver error classes and scenarios they had with prior upgrades and updates) before "passing" a big update like this as safe to RTM?

Most of what is being reported on here, are related to performance, but many of the driver related issues (AFAIK) are causing stuff to fail, rather than perform badly. My gut-feel for these issues, is that it is a complex interaction between the internal MS system services, since the "redesign" of search, to try to cut back on the Cortana integration, and some system are suffering because certain internal functions are fighting for resources when they should not be.

On a related note, I would really like the "AskPerf" MS blog/group to be more interactive on these performance issues, but I suspect not enough users know about  it to get the traction it needs. See:

https://techcommunity.microsoft.com/t5/ask-the-performance-team/welcome-back-askperf/ba-p/386881