To make a svn build (newest development version, may be buggy, but your job is to find these bugs and report them), follow these steps:
1. Make sure you have about 2.5GB free space
2. Download http://rm.endoftheinternet.org/~nexuiz/ ... System.zip
3. Extract it to somewhere
4. Double click build.bat and wait one or two hours
5. Double click run-sdl.bat or run-wgl.bat to play
To update to latest svn:
1. Double click build.bat and wait some minutes
2. Double click run-sdl.bat or run-wgl.bat
It will go much faster, as most stuff won't need redownloading or recompiling.
Note that your config and dlcache will be saved in My Documents\My Games\nexuiz, and not in the nexuiz folder this script wrote. If you are not a developer, do not mess with these folders - there is no user editable .cfg or the like inside! Do your own stuff in My Documents\My Games\nexuiz instead! config.cfg for example will be in My Documents\My Games\nexuiz\data, and you'd also put your pk3s in that folder!