Please note that the two links in the 'Mapping for winxp' doco are out of date and these are the new links - 

http://download.kingpin.info/index.php?dir=kingpin/editing/maps/map_editors/QERadiant/qe4/ 

http://download.kingpin.info/index.php?dir=kingpin/editing/maps/map_editors/QERadiant/def/

Mapping for winxp is a good tutorial on how to set up your Radiant.

One change I suggest is:-

In the QERadiant picture in the doco under ‘Views/Rendering’ 
you will see the 4th one along is selected (the one on the end) 
I highly recommend using the 3rd one along.