Hi Derek,
It is a control panel applet, so has a cpl extension rather than the usual .exe or .com.
c:\windows\system32\deltacpl.cpl
I find it can be run from the Start|Run box, or with a right-click "Run As..." or even with just a double-click on the filename in Windows Explorer, just as if it were an .exe.
I have just tried changing the device for the Set Volume button to deltacpl.cpl, and then to the full c:\windows\system32\deltacpl.cpl and closing then restarting Wave Corrector and checking the change had been preserved. Unfortunately although the change was preserved, clicking Set Volume still didn't have any effect for me.
Using the info in the link at the foot of the article I tried setting the device text to
rundll32.exe shell32.exe,Control_RunDLL deltacpl.cpl
(Please note that the case, comma and spacing as above are essential.)
This actually works as expected from the Start Run box, but it doesn't work when the Set Volume button is clicked. As no error message is generated I can't take this much further because I don't know exactly what command Wave Corrector is attempting to execute - e.g. maybe WC already puts in a rundll32.exe before the contents of the device text box are placed on the command line.
This link may be of interest:
http://vlaurie.com/computers2/Articles/rundll32.htm
It explains how in XP rundll32.exe can be used to invoke control panel applets.
I hope this gives you enough info to take things further.