How do you start zbrush with a blank screen instead of the giant ball and the tools menu?
Make sure you make a back up of this first.
On windows xp go to
C:\Program Files\Pixologic\ZBrush 3.5 R3\ZScripts
and then open up the DefaultZScript.txt. There will be two lines. Take out the 2nd line and save it. Next time you start up zbrush the sphere will not be there.
The light box can be done in preferences. You may have to save your config. too.
Turn off your monitor.

To prevent the Polymesh sphere from being loaded at startup you will have to edit the startup script that is run each time ZBrush is loaded. Locate the Zscripts folder inside your zbrush installation which will typically be “C:/Program Files/Pixologic/ZBrush 3.5 R3/ZScripts”.
Backup the file “DefaultZScript.txt”. Next open the file “DefaultZScript.txt” in the Windows text editor Notepad and add // in front of the line that reads:
[If,1,[FileNameSetNext,“ZPLUGS_SplashData/SphereStartup.txt”][IPress,ZScript:Load]][pd]
Save the file and restart ZBrush.
The LightBox viewer can be turned off in ZBrush by disabling Preferences > LightBox > Open at Launch.