Its easy enough to change your network adapters MAC address once you have a Debian/Ubuntu system installed, but I needed to do this from within the Debian installer (Lenny beta 2), and it took me a while to figure out how.
Read how here
So heres the problem: my NICs default MAC address is (say) 01:02:03:04:05:06, and for one reason or another, I need it to be 06:05:04:03:02:01 instead. Furthermore, I need this change to be in effect while Im inside Lennys installer, so ifconfig is not available. Heres how I did it: