Windows XP - RegMon.exe: "is not a valid Win32 application"

[Bodenseematze]

I have a Windows XP SP3 (32-Bit) VM which is needed to make some old programs happy and tried to install MFileMon v1.6.1 (and v1.6.0) on it. I followed the instructions at the release page:

• I downloaded the .7z and extracted it to a directory
• I then copied the DLLs mfilemon.dll and mfilemonUI.dll and the regmon.exe from the "Win32\release" directory to "%SystemRoot%\System32"
• I then opened a cmd window and changed my directoy to "%SystemRoot%\System32"
• Finally I tried to execute ".\regmon.exe -r" (of course with admin rights).

An error window opened saying that "C:\WINDOWS\system32\regmon.exe is not a valid Win32 application."