What does the Sleep with a value of 0 do?

>How about something like this (from AVFP PostSetup):
>

>=PostMessage(hWindow, 16, 0, 0)
>DO WHILE .T.
> IF WaitForSingleObject(hWindow, WAIT_INTERVAL) != WAIT_TIMEOUT
>	EXIT
> ELSE
>	Sleep(0)
> ENDIF
>ENDDO

>>I've created a little program that uses FindFirstChangeNotification, FindNext ..., and WaitForSingleObject to monitor a directory. When a file is added to the directory, the program comes to life and converts the file, zips it and moves it to another directory before resuming its monitoring of the directory.
>>
>>I had in mind that this would launch at startup on the users machine and just run all day but I'm seeing the need for the user to be able to pause or stop the program.
>>
>>Because the program has no UI, I wanted to just add a icon to the system tray and allow the user to double click the icon to pause or stop the program. The problem I'm having is that once program goes into it's wait mode, my icon becomes useless. Double clicking does nothing at that point because my program is off waiting. I could cut down the amount of time that the WaitForSingleObject function waits but won't that eat up a lot more processing time? I don't want this thing to be a resource hog.
>>
>>Any ideas on how I can accomplish this? Thanks in advance for any ideas!
>>
>>Rodd