hello, Mr "screwing around with blockland on random systems for fun" here:
blockland v0002 can be run on windows 95 and later. it will legitimately run on a high-end 486 and a voodoo2 (note I tested using an emulator but the result should be reproducable using real hardware).
blockland v21 ever since the whole key incident that made the game steam only can only be run with windows 7 and later. v21 revisions before this can be run in windows 2000 provided you add some updated DLL files to the game directory or use an extended kernel. I even wrote a guide on the former method some time back:
https://queeba.industries/guides/bl2000/bl2000.html. I haven't tested v21 with kernelex but I have my doubts that it would run anyway.
the oldest hardware I have managed to run v21 under had an 800mhz intel Celeron (basically a pentium iii minus some of the cache) and 128mb of memory running windows 2000. there were texture issues as the integrated intel i810 accelerator only had like 16mb of vram and the game would also end up crashing once you placed a single brick but it did at least run. I also recall testing with a voodoo3 and getting similar results.