Here's a quick hack using AutoHotkey from
www.autohotkey.com.
DimInactive creates a window, sets it's transparancy and changes it's region to surround the active window, thus dimming everything else.
Edit: Download and install AutoHotKey. Save the script as DimInactive.ahk and doubleclick to run.
Skrommel
;DimInactive
;Dims inactive windows
;Skrommel 2005
Gui,+Owner +AlwaysOnTop -Disabled -SysMenu -Caption
Gui, Color, 000000
Gui,Add,Picture,X0 Y0 W%A_ScreenWidth% H%A_ScreenHeight% gCLICK,
Gui,Show,NoActivate X0 Y0 W%A_ScreenWidth% H%A_ScreenHeight%,WINDOW
WinSet,Transparent,100,WINDOW
LOOP:
Sleep,100
WinGetActiveStats,wint,winw,winh,winx,winy
winw+=winx
winh+=winy
If winx<0
winx=0
If winy<0
winy=0
If wint=
{
winx=0
winy=0
winw=%A_ScreenWidth%
winh=%A_ScreenHeight%
}
WinSet,Region,0-0 %A_ScreenWidth%-0 %A_ScreenWidth%-%A_ScreenHeight% 0-%A_ScreenHeight% 0-0 %winx%-%winy% %winw%-%winy% %winw%-%winh% %winx%-%winh% %winx%-%winy%,WINDOW
WinSet,Top,,WINDOW ; Rem this line to keep the task bar visible
Goto,LOOP
CLICK:
WinSet,Bottom,,WINDOW
CoordMode,Mouse,Screen
MouseGetPos,mousex,mousey,mousewin
MouseClick,Left,%mousex%,%mousey%
MouseClick,Left,%mousex%,%mousey%
WinSet,AlwaysOnTop,On,WINDOW
Return