In the post Modifying Quake3, I have explained how to compile the Quake III source code. In case you are not using Visual Studio 2003 but using developer studio for VC++ 6.0, here are some tips to compile using that.
If you are using VC++6, download the tool :
prjconverter (Search on Google and you’ll find it)
Copy that in your Quake 3 code sub-directory.
Open up a command window. Change directory to Quake 3 code sub-directory and type.
It should make some project files.
Now load up Quake 3 code in VC++. Click on Projects –> Active Configurations. Change it to Win32-Release.
Unload the UI Project, it can create problems while compiling. Make sure that the Quake 3 project has botlib and renderer as its depedencies.