Although official Virtual PC additions should work with old kernels...it might not be stupid idea to try compile more modern Debian for Virtual PC "Pentiium II hardware" and forget additions for that version.
Or two virtual machines: an older Debian one with additions, and a newer one without. Recompiling things to target "Pentium II with MMX" is a good idea!
Personally I am very interested in Debian 6 and 7: Kernel is deblobbed from spyware-friendly firmware, and they don't use systemd by default like they do starting with Debian 8. I also have no respect for Debian 8, a release that officially supported PowerPC, yet did not provide 8.11.1 for platforms beyond the usual Intel/AMD/ARM CPU spyware stack (meaning PowerPC, MIPS etc. stop at 8.11.0 as far as official releases go). And starting with Debian 9, PowerPC got discontinued and moved to "ports". Although for Virtual PC purposes we can look at Debian 9 and beyond, naturally.
Anyway, let's see what we can do. Currently I'm creating a "Debian archive" of all those notorious "Jigdo-reliant" ISOs, getting them ready for upload on archive.org (for ALL jigdo-downloaded files and CPU architectures) and some key releases also on Macintosh Garden. This way we all can have easy, reliable access to ALL Debian releases. It will take some months, because the jigdo mechanisms suck and are unreliable and not all libs that make up the ISOs are available at all times, although I do see how it greatly preserves bandwidth.