Windows 10: Having to BACKDATE Win10 X64 Pro To Version 2004 From 20H2...

Dear TenForums:

here again - as I've found that SOME sort of "Windows update" this autumn has rendered by IMSI Design-published copy of DesignCAD 3DMax v.25 (dating from 2015) to no longer access files I HAD been opening and editing as late as the end of this past summer...and, even into the very early autumn...I needed to create a Win-10 X64 ISO-bearing thumbdrive to be able to BACKDATE my copy of Windows 10 X64 Version 20H2, back to the early-2020 timeframe "version 2004" edition to be certain either my DesignCAD 3DMax v.25, or even the recommended "DC" 3DMax Version 2020 update (only a US $70.00 cost to upgrade), can even be able to SEE the contents of my DesignCAD drawing files, let alone access them again. All I ever got in File Explorer after "the trouble" started, was the small square "red-x advisory window" that read "Invalid flag attribute" text in the window with the older v.25 software version starting sometime this autumn, I can't "exactly" remember when, so it HAD to either be the CAD software being "too old", or something going haywire with my current v.20H2 Windows install.

As one trial way I attempted to use to giving my DesignCAD drawing files a chance to be accessible once more, was to "use the 2-week free trial" of the DC 3DMax Version 2020 software, I gave that a try this morning...IT installed successfully on my Win10 64-bit version 20H2 installation, but it still COULD. NOT. SEE. the drawing files. even in my uncompressed, "direct-copy" backup thumbdrive...so I KNOW, now, that something in Windows 10 X64 v.20H2 IS "amiss", and I DO need some help in "backgrading" it to the 2004 version of 64-bit Win10.

I just used Itechtics' page for "How to download any Windows 10 version" and that page's attendant batchfile, and replaced an older, 2019-vintage version of Windows 10 that my "WIn-10 Version update USB thumbdrive" HAD the files for, with the early-2020-timeframe "2004" version, so I'm HOPING that can return my Win-10 install to a usable level for troubleshooting my DesignCAD software "challenges" to be able to get that great drafting software going again, in either the old v.25 edition, or the newer Version 2020.

I ONLY want DesignCAD to "be usable" again, as that title is the MOST important program on my entire computer.

Hope to get some tips on the PROPER way to "backgrade" my 20H2 install to 2004, retain as many of my programs as possible (the programs on the second, "D" volume of my "C & D" twin-volume SSD drive), unplug the data cable on my "E:/ volume" Seagate 500 GB hard drive to keep ANYTHING from being affected "there" (data ONLY on that drive) while "doing what's required" to get back to be able to re-install v.2004 of Win-10 X64, and then once v.2004 is "back on" and functioning, do a new install of DesignCAD to be certain my files are once again accessible, and "get on" with things once more.

Thanks in advance and Yours Sincerely,

:)