While you can run VB6 on Windows 8.1, this will not be good, and there will be many problems.
The smartest way to use VB6 in Windows 8 is to create a virtual machine using Hyper-V Manager , install Windows XP *, Visual Studio 6, MZ-Tools, and any other support software. Remote desktop on your virtual machine and you will go well.
In addition, when windows 9, 10 and 11 appear, your virtual machine can be transferred to them or to a new PC without violating the VB6 development environment.
* Or Windows 7 32 bit if you need to, but XP is better for VB6
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