Why linux (nv drivers) works on faulty hw

os linux drivers sometimes works even when the hw is faulty (when it shouldn't)
Had one gf4mx440 (elixir or something) and one day stoped working on windows (no hw acceleration even after driver/os reinstall) took the userlinux livecd http://hams.com/Mirror/userlinux-live-0.2.iso and booted .Was in the state of shock every thing worked (hw detected) , i could watch divx movies ...etc
Ok when i booted from the hdd (debian-sid) it crashed (black screen no signal)
What puzzled me was why it worked with live cd :) I know the board is dead (it will be replaced at vendor)

And the new nv linux drivers!
Just installed nvidia driver on my "borkstation" (userlinux aka debian-sid)
works great (gf2mx400)

And look what they have done with the new drivers ! :)
http://planet64bit.de/modules/news/article.php?storyid=351

Interview with NVIDIA Engineers
http://www.linuxquestions.org/questions/showthread.php?s=&postid=1285190