Clive, if you want to dim the whole screen may I suggest trying DarkScreen - http://www.fxc.btinternet.co.uk/assistive.htm
Variable screen dimming and simply close to return to your previous settings.

skwire,

Thats correct regarding modifier keys.  A friend is trying to help someone who uses a screen reader called JAWS, and who can only use one hand.  The JAWS action key can be set to either the Insert or Caps Lock keys, but using Caps Lock causes a few issues ref one handed typing.  As the user needs to press and hold the JAWS action key, whilst pressing another modifier key, the StickyKeys action would provide a one handed method of achieving this without some strange contortions when typing one handed.  Hope this clarifies the purpose of the request.

kip

One I recommend quite often is Yadabyte Subtext, quick, easy, free and portable if required

Yadabyte Subtext