How to install Office 2021 on Windows 8.1:

1. You must have installed Windows 8.1 (it can be both 32-bit and 64-bit), this workaround won't work on Windows 8.0 and earlier as of now

2. Have an extracted C2R copy of Office 2021 32-bit/64-bit (it must be Professional Plus and/or Visio Pro and/or Project Pro) handy

3. Install OfficeC2RExtender

4. Copy wotok_mdl.cmd to the root of Office 2021 C2R folder

5. Run wotok_mdl.cmd (no need to run as admin as it will ask for admin privileges itself)

6. Select option 3

7. Select default option

8. Select option 64 (if you have 64-bit copy) or 32 (if you have 32-bit copy)

9. Select option 2 (if present, if not, select option 1)

10. Select default option

11. Type "ProPlus2021Retail" (if you installing Professional Plus) or "VisioPro2021Retail" (if you installing Visio Pro) or "ProjectPro2021Retail" (if you installing Project Pro) P.S. The Volume variants are untested, so, I strongly recommend you to choose Retail ones

12. Select default option

13. Press "1"

14. Wait till it will be installed

15. And you should get this:

16. If you got this, then voila, you will get fully working Office 2021 (except for automatic updates, but that's not critical)

Office_C2R_Extender_W81.zip wotok_mdl.cmd

Edited August 24, 20233 yr by Cockatiel
I now tried it on 8.0 and I could not get it to work due to the installer throwing an error

The files are unvailable, please fix this