for older versions of software like Vocaloid 1, there are some things to try:
1) install the NET 3.5 Framework and try the compatibility tool of Win10/Win11, just right click on the .exe file, Properties, choose the Compatibility tab and select "Windows XP" or "Windows 7" from the menu
2) create a Virtual Machine with free software like QEMU or VirtualBox, and then install on it Windows XP or Windows 7(think of it like an advanced PC emulator):
www.qemu.org
www.virtualbox.org
3) if you use Linux, install Wine, which is very good for using any Windows application on Linux, and I know that many Vocaloid software works well with Wine:
Open Source Software for running Windows applications on other operating systems.
www.winehq.org
4) another alternative might be using ReactOS, a free open-source project developed since 1996 that is basically a reverse-engineered version of Windows, so it can run most of the applications and games:
ReactOS is a free, opensource reimplementation of windows
reactos.org
5) or the easier thing to do, go to Ebay and buy for cheap an old used laptop or office pc with Windows XP/Windows 7