Before getting into this, here's the usual page of things wot I have made. I've also written an article for EXE on the subject of Lego software.
As you'll know if you've visited Lego Mindstorms Internals, there's a community of code hackers doing interesting things with the RCX. One notable bit of work is Markus Noga's legOS (now called BrickOS), a replacement for the firmware. Markus gives a few instructions on building the GNU toolset to compile code for use with BrickOS, but assumes a unix system. While this is fine, I have to confess I generally have Windows 95 running instead. I discovered that you can build a similar cross compiler for Windows.
I used to have a description here on how to build BrickOS under Windows: however it was so out of date as to be useless, and other people have been much more rigorous in keeping up to date. I suggest you have a look on SourceForge or search the discussions on LugNet for more information
Last modified on 10th March 2004